Thank you for the write-up, I enjoyed reading it. It's almost impossible to find proper stats/methodology in testing things like tire warmers.
Maxxem is still making warmers, in Canada he sells through his website and Pro6. He is still using the same heating elements as the older warmers since they are proven reliable. I don't believe I've seen people using warmers older than 6 years that aren't a set of Bickle/Maxxem and are used for 15+ days a year.
He has mentioned to me in the past that the best thermostats he can source are only good for about 100,000 cycles, or 3-4 seasons of track. If the warmers are rated for 80c, after the thermostat is spent it will dip down and stabalize at around 50-60c. Having Maxxem replace the thermostats could give old warmers a bit more usable life.