What do spammers do when tarpitted?

Lots of them disconnect at around 400 seconds (this is how long it takes to go through the entire smtp dialogue at 1 byte per second and get a 451)

Some disconnect at 120 seconds - a significant amount of spammers time out after 60 seconds

Another blip at 30 seconds

However, Lots of them disconnect after a few seconds - once they notice they're being tarpitted. This did not happen as much for the first year or so. We'll come back to this later, and make good use of it.