Lately I am getting a lot of registrations from users that are obviously just bots. It’s annoying to have to go through and delete them. They, of course, never appear to fulfill the registration process fully. What happens if I just leave them? Do they get deleted automatically after some time period?
Yes, they get automatically deleted if they don’t activate their account. The relevant setting is purge_unactivated_users_grace_period_days and if it’s not set to 0, they get deleted, eventually.
Just to add, the default is 14 days, so unactivated accounts with no posts will be automatically cleaned up after that period.