Full disclosure: Like @Kaydreamer, I just started my own comic in the past year, so I'm not coming off of a long break, and therefore I can't speak to that precise experience.
However, starting a long project for the first time and getting back into the saddle after being away for a long time share a common problem: it's easy to throw yourself into it too hard, bite off more than you can chew, and risk burnout when you've barely begun. I knew that risking burnout from working too hard for a long time was a problem I might run into, so one of the rules I set for myself early on was to only do what I could sustainably, comfortably do on a daily or weekly basis.
For me, that means I produce one page a week. It averages out to anywhere from 1-4 hours a day, depending on how much time and energy I have, and what stage of the process I'm in. If I need to, I can not work on that week's page at all for a day, as long as I can finish it by my deadline. I've been following this rhythm since October of last year, and so far, it's been sustainable. I'm not left aching or drained when I stop drawing for the day, just satisfied that I've done a meaningful amount of work. I have time to work a part time job, do chores, and relax. It's working for me. If it ever stops working for me, I'll reevaluate what's sustainable, and adjust from there.
Find what's sustainable for you. Get into a rhythm, make a routine. I didn't used to be the kind of person who drew nearly every day (even though that's VERY common advice), but now that I almost have to in order to get a page out per week... I find that I sort of MISS drawing on days where I don't. And drawing almost every day for almost 11 months now has had a very positive effect on my art, too.
Oh, and I second the point about buffers, too. That's free peace of mind. Give yourself that gift before you start posting.