I would imagine the gasket would deteriorate and let the thermostat fall on its side. It would sorta obstruct the flow, but not hold it until it reaches operating temp. The thermostat is also a restrictor, slowing flow enough to accomplish heat transfer. Otherwise, if it just a matter of slower warm-up, I would be tempted to run sans thermo. I'm going to go buy some metal tubing to spin up in the lathe, and make a press-in shelf.
