I live by that rule.
If a tune hasn't grabbed my attention by then, it never will.

It doesn't work for ambient though. And what about albums that grow on you?

Personally, if I download a big discography, I'll put it on its own playlist for a while and spend a while listening to that one artist but on shuffle. If its overall good, then it all goes into the main playlist.

The main playlist is literally everything I have, on random. In this way I don't limit myself to tracks that have slow intros being destroyed in my collection, and I still manage to more or less listen to everything I have.

No time for ambient.
If it's a grower I'll have picked up on the potential anyway.

^

Yeah, I can definitely tell when there is potential and when I'm just plain not going to like something. I used to not be able to recognize that, but I've been music obsessed for so long now it would be sad if I couldn't.

The first thing is fair enough, but I think you're totally missing out.

The second thing...I can understand learning that to an extent, but don't you think its a little arrogant to assume you know everything thats ever gonna grow on you? I mean, that would imply you already know everything you'll ever like...

If you've got the space I don't really see the harm in archiving a collection, I mean just because you're not going to listen to it doesn't mean someone you meet wouldn't, invite friends over and tell them to bring their laptop or their own hard drive and let them browse through your collection and pick out what they want. I mean my dad left me a collection of old vinyl's but when it comes to my own child I'll most likely end up showing them what's on my old hard drive and give them music from my past that way.

Basically stop being selfish :P

I think I do know everything I'm ever going to like.
This isn't arrogance. More confidence with the type of music I enjoy based on my personal preferences and taste in music.
I don't think I'm missing out on anything that doesn't appeal to me exclusively.
Listening to music is a very personal thing, as I think you'll agree.
What I like may not appeal to a different ear and visa versa.
This doesn't mean I'm limited to certain types of music, although it is true in some instances.

After years of enjoying music I can confidently say that 20 seconds is more than enough for me to make an accurate decision on whether or not I will like that particular tune, irrespective of it's genre.
There are several prerequisites I use to determine if I'll like a particular piece of music.
I happen to think that the vast majority of music has all been done before, one way or another.
And with that in mind, for something to grab my attention it has to be original, or at best generic, but with a decent attempt by the artist/band of making a convincing effort at doing what has already been done before...their own.
There's no bigger turn off than hearing a new tune that I've heard somewhere before, with little to no attempt at being original. If you know what I mean?

As someone who's collection has been involuntarily annihilated twice, I dare not delete anything. Besides, I like scrolling over my music folder and observing the growing number of items held within it (for purely egotistical reasons.) But of course, that's just me and my stubborn ways. I share a different philosophy about music from the rest of the posters here advocating the '20 second rule', but I'm less experienced in listening to music than them and I still don't know why I like what I like or if I will like something based on a qualitative description. With experience this may change, or it may not. As it stands right now it takes time for me to form an opinion, but I'm not everybody, so go by your gut feeling I suppose.

You should really take some time to check them out before purging your whole music collection. My favorite is Harpur College Binghamton, NY 5/2/70. The acoustic set opening with Don't Ease Me In is really great.

Having said that, I've purged/lost my entire music collection quite a few times. I'd recommend it to anyone, especially if your just talking about hard drive space; Go for it. Rebuilding the collection is at least twice as much fun as never listening to half of the stuff you've managed to accumulate and allow to collect proverbial dust on your hard drive

I just have a folder called 'albums' (I have seperate folders for seperate tracks, compilation albums etctera). In this folder are folders with artist names and in those folders are folders with album titles.
Works for me. I don't mind not having heard everything.