I don't usually bother about how much is on my todo list. I tend to find that as long as I clear 3 items per day, I can keep it manageable. At the start of each week, I compile a list of things for my list. Before the start of each day, I'll say that need to do a, b, and c. After one week, that can amount to usually 18 - 21 items cleared off my list (depending on how many I complete!).
I don't tend to think about the list in terms of size. As long as I can complete bits of the list at a time, then I'm happy.
