Hosting Git repositories: how useful will git-gc be?

Hi,

I'm helping my sysadmin to set up some Git repository hosting via
gitosis. I'm trying to keep it as simple as possible.

A question: is it necessary/recommanded/useless to set up a cron job
doing a "git gc" in each repository? My understanding is that a push
through ssh will do some packing, is it correct? Does receiving a pack
trigger a "git gc --auto"?

Thanks,

-- 
Matthieu Moy
http://www-verimag.imag.fr/~moy/