> Once a team has a team leader the team leader can control the team members leaving the developer with simply 
> uploading the pot files and downloading the translated po files in a timely manner (once a week /month or so) and 
> merging them into the source packages as they would do anyway.

Ah ah! I was replying to this comment when I suddenly realized that my original thinking was at fault. The translated .po files do not need to be *patched* to GIT, they can just be *copied* over the older copies when new versions are submitted. This does not require any "manual patching work" and can be achieved quite quickly even by few developers.
In this view, daily updates would work fine.

Given the development rate, I still think that daily updates (or even weekly) would be overkill, since most of the time only the date of generation would change and nothing else. Probably by-weekly or monthly is a good choice.

Cheers
  Michele