archive_timeout, checkpoint_timeout

We want to use an archive_timeout of ~1min to minimize data loss in the
event of hardware failure (archive script includes external b/u).

archive_timeout only seems to work if it's >= checkpoint_timeout.

Could someone please explain in layman's terms the implications of using
  a checkpoint_timeout of ~1min as well?  Is it a bad idea?

We use PostgreSQL 8.3 on Windows.

Thanks,
Rob Adams