Transaction Id wraparounds

Hi,

What fast, efficient options are available for preventing
transaction Id wraparounds for a growing database (mainly
inserts). From the administrator's guide I understand a
system wide VACUUM or VACUUM FREEZE would perform the job
but for a large database (>10GB and growing) this takes a
long time to run. Only selective vacuums on the modified
tables tend to be more effcient. However, there are also
tables (for example tables that are no long updated but
have heavy selects on them) in the DB that aren't touched
by a vacuum in weeks (probably never). In such a high
activity database what would then be the best way to take
care of the transaction id wraparounds (for example, would
shutting off and restarting the db do the trick). Also,
what should be the criteria to check when this issue needs
to be addressed. For example in one of our
databases age(datfrozenxid) is 1076913425.

Thanks..
Amin