High checkpoint_segments

We need to do a few bulk updates as Rails migrations.  We're a typical
read-mostly web site, so at the moment, our checkpoint settings and WAL are
all default (3 segments, 5 min, 16MB), and updating a million rows takes 10
minutes due to all the checkpointing.

We have no replication or hot standbys.  As a consumer-web startup, with no
SLA, and not a huge database, and if we ever do have to recover from
downtime it's ok if it takes longer.. is there a reason NOT to always run
with something like checkpoint_segments = 1000, as long as I leave the
timeout at 5m?

Jay Levitt