Don't do them 
they are not something you really need unless characters have some complicated clothes.
Or think of it as if you're drawing pictures for a comic, not illustration 
A lot of people feel like they "ought to" do a reference sheet for their characters, because they've been behind the scenes stuff for animation and games and so they think it looks professional to have one. The thing is though... a reference sheet is something that's more useful if other people need to draw your character in your style, so they need a guideline for how you draw that face in profile, how you draw the eyes in various expressions etc. You don't necessarily need this if you're working solo because you know how to draw in your own style.
Personally I don't do reference sheets. I'll do an illo and some rough sketches to work out things like the profile of the face or if there are any details on the character to remember that aren't on the illo and I'll probably make a palette, but I don't feel a need to draw all my characters in A-Pose or T-Pose from exactly the front, side and back unless I'm making a 3D model or somebody else is drawing them.
I gave up on making ref sheets because the same thing happened to me. I also just ... didn't enjoy making them at all and never finished them. Now I just sketch my characters in whatever situation I feel like sketching them, and create illustrations too, and that's a much more natural and enjoyable way for me to develop and refine my character designs.
Some artists can do this more systematic prepwork really well and it helps them, some actually need it, but not everyone is like that, and that's okay. My workflow is much more chaotic but it still helps me develop my art, characters and stories, so I'm not overly worried about it. And if you can already draw your characters well, as your illustrations suggest, then you don't really need a ref sheet. You could even just paste all your illustrations of one character into a file and turn that into ... something like a ref sheet to go back to if you don't draw a character for a while or forget what certain details look like or whatever. Maybe even add some blobs of the main colour you used around them if you didn't save them in a palette already. But you really don't have to.
Like a lot of other people have already said, I don't really do much in the way of a proper reference sheet either. If I have to do something to reference, it's usually just for the character's costume, not the character themselves. I'll do a front and back view of their outfit so I don't miss any details, but for the characters I usually do a handful of concept drawings until I get the design nailed down, then call it a day.
All I do for ref sheets is a front view with colors I can pick from. No fancy turn arounds or bios. I keep it personally to keep them on model and not have to keep hiding the shading layers to color pick. It's up to you honestly. I have shit tier memory so I need one but if you can remember your characters perfectly, its not worth it.
Reading all of this makes me feel a lot better. When I first started my comic, I did have reference sheets, but since the style change I had made new ones. Fortunately, it wasn't really a problem, but I always thought needed to make more. But as far as they're concerned, only make them if you need them, and you'll be able to tell if you need them.
I'll go against most of the sentiments on the thread and say - do it but only as far as you think you need to. I have terrible memory and constantly forget parts of my characters (and sometimes the colors on them don't display well on the artwork), so I always check on my sheets to make sure I didn't draw the wrong pattern or something. However, I started with full lineart, pretty, presentable... And that just takes too long for something that's basically for me or fans who really want to see all the production. So my sheets now are with my sketching brush, no shading, and I don't necessarily need to draw every outfit change or alternate form.
I have examples below, but just to show it's not really rendered or super detailed. You can just do sketches for alternate forms, or a quick study of the ouftfit, and no need to organize it on a big reference paper either.
It's your comic, so even the productions need to fit to your needs. Not doing them at all, or just doing what's comfortable and you know you'll want to check later quickly.
As long as you create several drawings each of a character, you can compile those as your ref sheet. I know that's what some people like to do.
I personally love ref sheets. But if you don't want to make one that's oaky, it's your comic, and there's no "wrong" way to do it.
I just make a drawing in a weird pose. Maybe practice some faces here and there, but not a reference sheet with standard rules. I use all those practices as a reference. In my webcomic I am posting on the last page the first drawing of the characters, that I kind of used as reference for a time. Now I surpased that models, ha!
Here is the example.
I mostly keep references if I'm requesting commissions. Just a basic front and back with flats.
Outside of that, I do conceptual art instead. That includes character interactions, scenes, and gestures. It helps me create stronger characters and actually apply the traits I give them. Also helps with plot development.
Eh, I don't find it useful. I create one concept drawing to hash out how I want them to look, then I use that as my reference and any other drawings I did of them
Only tip I have is borrowed from @Inspector_Spinda , which is to create horizontal rules through key points (eyes, nose, outfit details, etc.) to help with proportioning in different angles and to keep things aligned properly. Or, if drawing digitally, you can also opt to use a single one that you can just move up and down on its own layer.
I've not really made character reference sheets myself in the past, as I've always been of the mind "I draw the main characters so often I don't need one to draw them, and side characters appear infrequently enough that I can keep them on model by just looking back at prior instances." Buuuuuuuut I'm finally going to make some turn arounds for the cast of my current comic once I reach their outfit revisions a few episodes away 
I've been finding that I have a lot of trouble keeping some details straight, such as the knight's armor which is complex enough that it appears slightly differently in just about every single panel... I also can't always easily fabricate everyone's hair styles from atypical angles and the like. It just seems like spending the time to make a ref sheet may be worthwhile~
Oh, sorry, it's just short for "illustration", I get so used to using that term I forget not everyone knows it!
I've never dona a reference sheet in my life. I'm not gonna bash them and say they're useless, but it's not something you can't do without. To me, the most important thing in a character is if they end up looking how you wanted them to look, not absolute consistency. Just take a look at the Naruto manga, it probably has the most consistent art I've ever seen in any comic, but it's pretty mediocre overall.
My "reference sheet" Is just whatever panel I drew that character in last that I thought looked pretty good. But when I'm doing studies of colors and clothes--I never do a polished ref for that. I'd rather save the polishing for the comic itself.
I don't make them. I tried making one, and hated the experience so much I decided I'd never make another unless I was being paid to do so. I know what my characters look like, and I'm the only person drawing them, so I really don't need a ref sheet.
I may end up having to retroactively do a few for portfolio purposes, should I start applying for comic illustration jobs in the publishing industry... but I'll just choose my easiest, favourite designs for that, to make it fractionally less tedious.
I didn't make them. To make a character, I just choose the best one from bunch of my doodling. For 'My Last Life', I tried to make one, but only the face from 3 angles views, that's all. I don't know if that still consider ref sheets. I figure I need it at least the faces since, I have hard time to have the same 'look' for each character when changing angles. If you don't have this problem, or you just draw for yourself you really don't need it.