I don't, and neither should you. :-) If an idea is worth pursuing, it reoccurs in several ways. For instance, with my current project I can have a casual conversation with someone around a pain point and instantly see how my idea could help. Many of my ideas seem brilliant when I first have them, but then fizzle the more I think about them. Even if they are wonderful and viable, your motivation to build them out is a…
I agree that many ideas seem silly after they've sat for a bit, but I disagree that you shouldn't keep track of your ideas. I get a lot of ideas. I keep track of them. If they fizzle, I remove them from the list. I simply don't always have the time to jump on implementation of the ones I consider "good" when I have the idea. Also, keeping track of them means that I'll basically never have a point where I'm going "hmm…
An idea you can't execute is worth about as much to you as no idea at all. The concept of an idea being so timeless that it will be both relevant and somehow forgotten in the future if not recorded is not one I accept.
Either your idea is so great that you'll a)make time for it or b) remember it in the future, or it probably isn't as wonderful as you initially thought after all.
hmmm nothing to do, wish I had an idea!
A person who generates so many ideas that he's considering recording them won't find themselves in this position: You'll always have more ideas than time to implement them, so don't sweat it.
Not recording ideas is both a way of validating them and focusing your mind on implementation. "Idea people" like us can easily lose ourselves in the mental masturbation that is the generation of "ideas". The last thing we should be doing is encouraging staying in that stage longer than we have to.