checkpoint_timeout irrelevant in 8.1.9

According to the WAL config documentation correctly, checkpoints are created every checkpoint_segments log segments, or every checkpoint_timeout seconds, whichever comes first.  However, it seems as though setting my checkpoint_timeout has no effect on checkpoint creation ( I have it set to 30 seconds).  Forcing checkpoint by running psql –c CHECKPOINT mydb doesn’t do the trick either.  Checkpoints are created solely based on the checkpoint_segments logs reaching their configured size.

This is not satisfactory in a low transaction volume environment.  Any hints on how else can I trigger checkpoint?

Thanks in advance,

~george