Personally, I don't understand the GTD "waiting fors". Why review them all
regularly? What I do is, I consider each "waiting for" to be either an action I
need to take, or nothing in my system at all. I decide at the beginning how long
I want to wait before reminding the person or taking any other action in case
they don't get back to me, and I put a reminder in my tickle file for that date.
Sometimes at that time I'll change my mind and decide to wait longer.
If I would do nothing in case the person doesn't get back to me, then I just
forget about the whole thing, and when the person does get back to me then
it gets back into my system at that time (e.g. I might put in an action to reply
to the person again).
If a "waiting for" comes up in my tickle file and I've already received whatever
it is, I'll remember that, and just remove the item from my tickle file.
That way, I only need to spend time looking at that "waiting for" once.
If I was concerned that I wouldn't necessarily remember, then I could
cross-index in order to remove the item from the tickle file when I receive
the reply from the person; again I would only have to deal with it once.
What's the advantage of doing it the GTD way? I would think it would
foster a feeling of impatience rather than mind-like-water.