If you're just starting out its alright for it to take a long time to make the comic. It takes years of deliberate practice to get to a level of drawing fast and accurate.
I wouldn't worry about dissapointing readers if you cannot keep to a schedule. In my experience things tend to take longer than you anticipate, always. And things go wrong. Readers know this and Tapas community readers are exceptionally patient and understanding.
The readers are also outside of your control so you needn't let them control you. The only person I think you should be worried about disappointing is yourself.
If you want to start uploading to challenge yourself to draw faster and keep writing a good story then I say go for it! No matter how small, the likes and subscribes are encouraging.
Just be sure not to focus too much on getting readership. Your first responsibility is to the story. The second is putting the story where people can see it. The rest is out of your hands.
I would recommend one page per week, it gives you the biggest opportunity for exposure. Something that also works well is that your first update ought to be a couple pages, enough to tell a whole story beat or scene.
That will increase your chances of an editors pick or daily snack.
After that one page a week is just fine since its a long form comic.
Four pages a month might seem little now, but down the road it does add up and as you get more practice, you'll be able to increase your output! Making comics is a marathon and we all start somewhere the important thing is to get started and don't stop not matter how slow you go.
So don't worry. Just tell your story, put it where people can find it, and hope to touch the audience with it. It's all you gotta do.