On a regular basis? Probably somewhere between 1 and 5 percent. Over a course of a year? Probably closer to 50% or so.
I'm obsessive when it comes to music, and will buy some albums that I have a moderate interest in and only spin them a few times. I've learned to cut back on some just because I can try out some "new" artists online, like on youtube, and give them listens there before I commit to buying an album, but I only mainly buy albums by my core-set of favorite artists, and related off-shoots from them. (Un)Fortunately, many of them are very active and produce a lot of material on a yearly basis, so I'm constantly looking to see what's coming out in the next month or two and saving up to buy.
I try to listen to everything I buy at least once or twice after getting it, and if I'm not completely obsessed with it, it gets ripped, put onto my iTunes/iPod, and the CD gets shelved away for awhile, but I may revisit it on my iPod later on. I probably should start looking at selling some of my CDs, although they have some sort of "great investment" value to me, having spent earned-money on them makes me not want to get rid of them, but there are some albums/artists I could do without the physical discs for.
There's also the idea of Remasters - in the last decade, many of my favorite bands have gone through a new set of remasters, chief among them is Genesis, and while I spent the greater part of a year getting their entire catalog back in 2004-2005, I got the new remasters back in 07-09 when they all came out, so now I have two sets of the Genesis discography - the original CD Remasters, and the new ones from the Box Sets.
Now Queen is doing this, and Pink Floyd also recently re-released their entire catalog, and Rush is due to re-release their Mercury-era albums in 3 boxsets coming out later this month, which, being my FAVORITE band, is on the top of my list of purchases to make by year's-end, but I may wait til after Christmas (Money!) to get them.
I haven't gotten the Queen boxsets yet, nor the new PF re-issues, and I still haven't gotten the Beatles Remasters from two years ago (although I've been meaning to), so all these remasters/re-issues are kind of a drag on me, considering that most of the time, the packaging is lavish and the remastering is worth the cost, but at the same time, there is SO MUCH NEW MUSIC coming out, so I've been having to divide my music-budget in such a way that keeps my need for new music happy while being able to satisfy my urges to get all the latest-and-greatest products from my favorite bands, despite them being re-releases.
*Sigh* Slightly off topic, but ya know, it's all about my obsession with music. I try to dive into my iPod every now and then and pick a band I haven't listened to in awhile, and pick a random album and go "Oh...hmmm...haven't listened to this one in awhile. Let's have a spin..." and I rediscover why I got that album in the first place, but it's hard to do when one has over 800 albums...
-Marc.