I think I've seen as short as 6 minutes. If you have the tape is in the right cases and you have some sort of splicing kit, you can always make them custom lengths.
I've never tried the SM series tapes, but I think all of them (what little is left nowadays) are fairly lackluster compared to earlier versions of the same tapes. Maxell XL-II isn't what is used to be either.
There are some guys over at the Tape Heads board that are working on producing (or importing?) and distributing tapes. I haven't really had the chance to read up on the project thoroughly, but I guess it would be in my best interest to do so, huh? I know Type II and Metal tapes are hot topics in those conversations.