Just last week, I've decided to finally document the current download methods for translations coming from localize.drupal.org at http://localize.drupal.org/download. We've set up translation packaging earlier this year and let it run while being monitored for tweaking. We found that we can run the packaging as often as every 5 minutes and with allowance to generate as many as a hundred .po files per run. With these numbers in mind, we can generate 100*12 = 1200 files per hour. But we have 67 languages and 12000 releases to generate .po files for, so that is above 800 thousand files to generate. If we'd need to regenerate all files all the time, it would take 28 days.

Looking at the database, we've generated close to 500 thousand files by now and the drush processes looking at generating more found that its time to update the existing ones instead. We do not generate .po files for language and release combinations where no translation exists, so 500 thousands versus 800 thousands is a good amount of files generated. Given we have all these base files now, all our drush jobs do now is they regenerate files as needed. With them being set to look at 100 releases at once (and sometimes still not finding any translations to regenerate), we seem to be on to regenerate files as new translations come in pretty fast (think days or even hours). We are still experimenting with different parameters and ways to speed the process up, but it looks promising.

Let us know if you have any feedback on the downloadables and especially if you have good/bad experience with http://drupal.org/project/l10n_update, which I'd suggest you try out to automate the flow of getting translations for your sites.