...I think I know what you mean, Volgadon: I've heard about poets, e.g., publishing young, and spending much of the rest of their career correcting things published. I was in my late 30s, and only make minor changes when I read/study my life's work annually.
As for publishing music on myspace, etc., I (as with most, I think) practise the piece until I feel I'm not going to get it a whole lot better, then record/publish/have a go!