This problem is exactly why I gave myself a deadline for when I need to get character designs done. It just goes on forever if you let it. :'D (And I'm glad to see I'm not alone in finding ref sheets a huge drag X'DD)
As long as I can clearly tell a character apart from another, that's all I do before chucking them into the story. You can always change little aspects of someone's appearance later anyway, if you want to. (My trick tho is just to leave it until the end of my deadline, cuz then I'll /have/ to decide. X'DDD)
It takes me roughly 10 hours to do one page, split across 2 or 3 days most of the time. So around 5-3 hours per day. I spent about 3months planning, but was messing with 3 different stories at the same time.
To make it seem less like a chore, you need 1. figure out how long you can actually work on a page before burning out, and 2. what can motivate you to finish a page.
If you can figure how much you can do before getting bored, and how long you take to recharge, it's easier to make the best of your time. Thinking about good things that will come from you working on the comic also helps you enjoy the process, since that's essentially what motivation is.