How about month-end exports? You can keep them for as long as you need, but there is the extra step of re-importing them to be able to restore from them.
When I'm confronted by someone trying to do a "traditional" full-incremental-incremental scheme with TSM, explain how TSM works, starting out with, "Unlike every other backup program you've ever used, TSM..." (And I seem to have to use that speech a lot...) Nick Cassimatis [EMAIL PROTECTED] Today is the tomorrow of yesterday.