How often are superceded packages removed from PPAs?

Is there a schedule for how often the purge superceded packages job runs? ideally i would like to find a way for us to still be able to do daily builds and avoid having to resize our PPA's constantly because we make a new PPA for each new version of the software. we keep them separate to avoid forcing people to jump up to a new series if the current one is stable.

if it's like a once a day thing and we're just barely missing it or something, then maybe we can adjust our cron that uploads the daily build by a few hours etc.