Today I heard from my hosting provider that last month, the site went over its bandwidth allowance. Looking into this I found some scripts that were excessively checking for updates, resulting in hundreds of gigabytes of daily bandwidth. Looking at the code for these scripts, it appears they checked for updates every time the script executed.
So starting right now, scripts must only check for updates after a reasonable period (1 day?) has passed since the last check. Any script I find making excessive requests will have its update URL blocked until the issue is fixed in its code.
If anyone has any example code on how to correctly perform update checks, that would be useful.