recovering from "too many failures" wal error

All;

We have a postgresql 9.2 cluster setup to do continuous wal archiving.
We were archiving to a mount point that went offline. As a result the db
could not archive the wal files, we ended up with many many errors in
the logs indicating the file could not be archived:

WARNING: transaction log file "0000000100000FB100000050" could not be
archived: too many failures

So we caught the issue before the file system filled up, fixed the mount
point and I see wal files being added to the target wal archive
directory. However the pg_xlog directory does not seem to be shrinking,
there are currently 27,546 files in the pg_xlog directory and that
number is not changed in some time (since we fixed the mount point.

I assume the db will at some point remove the backed up files in the
pg_xlog dir, is this true? or do I need to intervene?

Thanks in advance