As one who can change projects between the sewing machine and the ironing board, I devised a system. If something has a deadline, it gets assigned a block of time every day that will see it finished. I choose a project that's getting stagnant and assign it 20 minutes a day. Otherwise I'm a will of the wisp, working on what I feel like.
Short answer: Never too much and future generations will finish what I don't get to. Besides I finish more than most people ever start.
By the way MG, where are those yard sales. Never see anything like fabric around here.