>Hmmm, I'd be pretty upset if I was in the middle of something at some odd
>hour, like high noon or 4 in the morning, and /tmp went away.

obviously you only remove things on order of a few days old.

All usage is problematic if:

/var should never fill
/var/tmp/vi.recover should seldom be nuked
/var/mail is HIGHLY important

Solution is to throw more disk space at the problem.  Or link /var/tmp to
/tmp and accept that you'll lose vi.recover over reboots.  The i386 limit 
of 5 devices per disk doesn't help either.