In my experience it takes about a year at a new shop for me to train the office staff not to try and make me do free work. Yeah I know you’re sick of hearing me ask about labor, either fire me or pay me to do my job.

Stuck closed thermostats are very rare and difficult to diagnose. Any “shade tree mechanics” on here claiming otherwise probably misdiagnosed or accidentally solved the real problem which was low coolant or something that would have been taken care of during replacement.