Well, I only work on one project at a time, but that is just me and I would never tell anyone else they should sew the same way I do. I can't, however, spend a great deal of time at it. I find that about an hour and a half is all I can sew in a row, maybe two hours if I "just have to finish" a block or something.
We are all just different, and that is what makes it fun!
Dina