Checkpoint segments

If I have a system that writes out one WAL file every 5 minutes, and I
have these settings:

checkpoint_timeout = 3329
checkpoint_segments = 1000
(parameters checked as valid via pg_settings)

How many WAL files would you expect to see in pg_xlog, once the system
has reached steady state?

I would expect checkpoints to occur every 3329 seconds, giving on
average 10-11 WAL files per checkpoint. So, I expect to find up to 23
WAL files in the pg_xlog directory.

I have 308 files in pg_xlog, which remains constant. The oldest file
time is approximately 24 hours ago.

Am I just tired, or is that a little strange?

pg 7.4.6

Best Regards, Simon Riggs