Too many WAL(s) despite low transaction

Dear All,

We just migrated our system from Informix/GeneroDB to PostgreSQL 9.03. We
are monitoring the situation very closely.

Everything seems to be OK except our concern on the build up of WAL files.
You see, we cut off from the previous database around 3.30AM. After that we
directed our applications to point to PostgreSQL. We already had a Standby
machine A up and running as a Secondary for log shipping and replication. We
also setup another machine B just to receive the WAL(s) and store it for us
to backup later for recovery purposes. As there are no PostgreSQL running in
that machine no pg_archive_cleanup is in effect. Our plan is to backup the
WAL(s) every 12 hours and then purge them all. But at the rate the logs are
building up at machine B, we would possibly ran out of space very soon.

But this is the point to note. There is very little transaction taking place
and the checkpoint_timeout is set to 35minutes. Despite that the WAL logs
are getting shipped every minute.

Any clue as to what could be the problem?

Thank you.

Regards,

Selvam