What is the natural state of a TODO list? Is it naturally empty, always growing or always in motion? Your one true TODO list will never be really empty, and it shouldn't just sit stagnant, ever-growing and eventually ignored. It needs to be in constant flow, like a stream of water, with new items coming in and done items going out. Your list will shrink and grow sometimes, but on the whole it will probably remain about the same size. The particular items on the list, however, should definitely change, and technically (according to the Getting Things Done method) nothing should stay there longer than two weeks. That's a real trick, and I certainly don't have it down.
Mokalus of Borg
PS - That's what weekly reviews are for.
PPS - I haven't made time to do them lately.