I like the idea of the system determining whether to run it or not by default, but being able to force it on or off.
Maybe a makemandb_force=YES/NO, defaulting to NO.
If makemandb_force=NO then the makemandb will be skipped iff
- Memory is 64M or less
OR
- man.db has been modified in the last N hours (24? 4?)
This does mean on a small old box which is never run overnight makemandb would never be run, but I think that is a reasonable edge case - and in fact I'd prefer that behaviour on my small old boxes :)