WAL Archiving frequency

I've setup WAL file archiving to my SAN storage over the network (using an NFS mount to the file server).

I've noticed that it's archiving the 16 MB wal files about once every minute. Is this normal? There's a huge number of files in my wal_archives directory now.

Is there a parameter to tell it not to archive so frequently? Or is this nothing to be too concerned about?

Thanks,