S.B. suggests that generations could be tagged so they aren't automatically deleted.

1. Unforgettable generations -- In scenarios similar to the above, I would also find it useful to be able to mark certain important generations as "unforgettable". That way, when I run an automatic time based forget command, I can be sure that it will preserve certain milestone generations, even if they weren't the last generation of the month or the week or the day or whatever.