Avoid WAL archiving when idle?

I have WAL archiving setup on Postgres 9.3.2 using WAL-E on CentOS 6.4
using the postgresql.org RPM. This is working fine, except I see a lot of
spurious activity in the S3 bucket with wal files being backed up every 5
minutes even when the database is idle. This can make restoring to a dev
server really slow if it's been a long time since the last base backup. The
only non-default configuration is:

wal_level = archive
archive_mode = on
archive_command = '/usr/local/bin/envdir /etc/wal-e.d/env
/tools/python/current/bin/wal-e wal-push %p'
archive_timeout = 60

The 5 minute interval matches the default checkpoint_timeout, so I guess
I'm seeing the same problem as mentioned here:
http://www.postgresql.org/message-id/CAMkU=1wCyN7JNOTXCnCqpULtzNfV8ZWH5BqrqZhA+uGB1x-fTA@mail.gmail.com

Is there anyway I can configure PostgreSQL to avoid continuously archiving
WAL files while idle but still place a limit on the time until a database
write is archived?

Laurence