I like how on a single-node I can utilize data compression and get a 95% storage saving.
In subsequent releases, we'll add full support of compression, e.g., just create a compression policy on the access node and you are off and running.
compress_chunk operates on a single chunk, the way to define "compress all chunks older than 1 week is":
SELECT compress_chunk(i) from show_chunks('conditions', older_than => INTERVAL '1 week');
So you'd need to setup a cron job that runs that script every night or something...at least until we release compression policy support.