Warm-standby robustness question

Hi,

We have two PostgreSQL 8.2 database servers: A master and a warm-standby
server.  We plan on making an initial backup of the master onto the standby
and then use log-shipping with "real-time" WAL-file processing as described
in http://www.postgresql.org/docs/8.2/static/warm-standby.html

My question is this:  If the master database is fairly busy, gets
VACUUMed once a day, etc. can we expect the warm standby server
to work correctly after days/weeks/months/years of log shipping,
or should we periodically take new base backups?

How long would you go between base backups?  Or is one initial copy
really sufficient with WAL-shipping-and-consuming working perfectly
thereafter?

Regards,

David.