First of all I would like to thank you maintainers for this module. It's working nice and is really a great tool for webmasters.
Forgive me the catchy title, but there is a performance related issue I would like to know more about.

I wonder if there is a way of checking for updates via some sort of "aggregated-per-project" way and ditch the per-site queries. I peeped the code and saw in a comment that this has to be made per-site. I wired in about 20 clients to my server instance and its cron runs for at least 6 minutes while fetching all the project update info for all client sites. I can imagine how long would this last if I configured hundreds of clients... this seems such a resource waste to me.

Disclaimer: I have no inside experience about either update or update_status_aggregator module, I just wanted to open a discussion about how could this be improved somehow.

Any thoughts?