amount of WAL logs larger than expected

We run postgres 9.2.12  and run vacuum on a 540GB database.

I've attached a 'show all' for your reference.  With CHECkPOINT_SEGMENTS set at 128

and CHECKPOINT_COMPLETION_TARGET set at 0.9 I wouldn't expect the number of logs in pg_xlog to creep much over 400.  But when we run vacuum, the number can climb to over 5000 and threatens to blow out on space.  Is there something else I should be looking at causing this unexpected number of logs?

Our server is also master for a slony1.2.2.3 slave and also to a hot standby server.

Any insight /recommendations welcome.  Thank you

 

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