A bounty inside of a hopper or chest doesn't tick, meaning the timer doesn't count down. Combined with a hopper and a lot of waiting, it's possible to gather huge numbers of bounties to turn in all at once.

An 8 hour overnight AFK session will yield 240 bounties with default config settings.

Hey, I never quite thought about this. That's a very good point! I might make it like this:

1. Bounties can't be sucked out of a hopper
2. Bounties can be sucked out of a hopper, but their timers will start when that happens.

This is done for v3.0 as of a little while ago!