Mike,
In another post Joel brought up a good point about residual crud from the coolant over time depositing on the thermostats and possibly affecting their function. If you have used non ELC and it has not been changed or had proper SCA level maintained then there is an argument to be made for possibly changing out a thermostat preventatively. I have seen issues in poorly maintained vehicles including partially plugged radiator cores from antifreeze that was kept in service way to long. There has been pitting of components like liners with the use of older Non ELC antifreeze also. See page two in this link where they compare thermostats from ELC and non ELC usage.
http://www.toromontcat.com/pdf/ExtendedLife.pdfLiner photos here...
http://www.borusanmakina.com/doc/GucSistemleri/MusteriDestek/CAT-ELC.pdfWith ELC use, the need to preventatively change out a thermostat due to deposits, in the miles that we might travel in an RV, seems very unlikely.
Later Ed
