I'm practicing GTD for several years but I don't think it's really possible to have 100% of my commitments/projects/etc. captured, processed and organized unless all I'm doing are weekly reviews non stop all the time.
The problem with an incomplete system is that I don't fully trust it when it comes down to reviewing it and choosing what to do. I mean the most practically useful aspect of GTD for me has been keeping track of projects with Due Dates. Other than that I'm doing things which are not on my lists most of the time.
Here is a related quote from David Allen
There is a light year of difference between a system that has merely a lot of our commitments objectified and one that has 100% of the total. And few people have ever gotten to a totally empty head, with absolutely every project, action item, and potential agreement we have made with ourselves and others out and available in an easily reviewable format.I don't think you can keep the system 100% up to date at all times. Sure, you could keep it almost complete though but then according to David Allen it's not really worth it...Either your head is the best place to hold all your agreements with yourself, or it's not. (You can guess which way I vote.) I can't imagine any intellectual justification for halfway in between. Yet most people still have over half their life in their heads. And a partial system is almost worse than none. As a favorite mentor of mine is fond of reminding me from time to time, in regard to tracking and renegotiating life commitments in general, "99%'s a bitch, 100%'s a breeze.