I have only one main project which is very big and updates twice a week. However I intentionally draw everyday sketches just to keep myself in good shape. Also I have my Patreon with another short comics for fan service. And each month I do 5 to 10 commissioned drawings.
I guess the best thing about that is that I can switch my attention to different tasks and styles, which sometimes saves me from routine. But on the other hand I sometimes feel distracted because I can get inspired to draw my comics, but I have to draw commission.
In the past I've tried to publish two comics at once. One was my own work, one was made in collaboration with a writer. Physically I could do that, but my co-author got jealous that my own comics was more popular then our collabed one. He blamed me I didn't put enough effort into our collaboration. I took it a way too hard and put our collaboration on "hiatus" until I could draw better so he would be happy about it. But I tried to keep up with my own comics. As a result my co-author made everything so I would feel guilty about that.
Finally I dropped both comics and don't even want to start them again. But that was a very good experience. With its help now I'm very thoughtful about my schedule and co-authors.
I guess the best thing is to work on as much projects as you are able to without damaging yourself physically and mentally. If you enjoy both at once that's perfect and you have nice stable speed of drawing