When I mix a project, they get the mixes (but not the sessions) and the project is done – it’s their responsibility not to lose them. As a courtesy I keep everything archived, but it’s just a courtesy, not something I warrant. If I’m producing they get the tracks as well, but again, I keep an archive as a courtesy. I don’t really do straight tracking sessions, but if I were to do so, same thing. I’m not responsible for losing data I keep as a courtesy (although I’ve never actually lost anything). The reality is that when the client gets their goods, it’s their responsibility not to lose anything. If I’m mixing a beatmix or mixtape song, I delete it after a few days; I see no point in spending my money storing stuff that I’m doing for ridiculously small amounts of money… hard drives ain’t cheap.
I used to archive everything onto DVD when the cost of hard drives was just too high. Ugh. I have boxes and boxes of archived projects in my basement, like a LOT. I keep stuff forever, or as long as the media holds up (sooner or later one of these discs is sure to fail, but it hasn’t happened yet, and some of these are oooooold). These days I buy USB hard drives. I just picked up another one last week J I don’t zip them or anything, that way I have access to them if I need them. Once in a blue moon it becomes handy to take a quick look at an old session for an artist and I can run them right off the USB drive (although high track count sessions won’t run very smooth, but usually I don’t need to actually ‘hear’ anything, just looking).
Anyhoo, I’m generally paid up front, so once everything is delivered it gets moved from the main drive to the USB drive.