they actually did 'break-up' (more or less) in 2003:
http://www.belowempty.com/articles.php?s=story&id=19 G1: So is this really the end of STP?
ROBERT: Well, we're putting out a record called Thank You! So, yeah. I'd have to say it is closing the book. Dean and Eric and myself, I think, all feel a sense of sadness, relief, anger, melancholy about it... but to try and go on and accomplish something with this band after we've already peaked is a bit cheesy. There's a cheese factor with guys hitting 40 trying to recapture glory. There's no way to go but out. If you're driving a car and it goes off the road, it's hard to steer that car back on the road. I'm proud to look back at our career. I feel we've made a valid contribution to music. I guess putting out a greatest hits set is cheesy, but the strength of the songs is there.
G1: So how do you feel about closing the book on this band?
DEAN: It was time to move on to other things. Life and personalities and brotherhood took its course. Everybody's got cool stuff going on. Scott is about to embark on a new experience. Eric built a nice home studio. It just ran its course, I suppose.