I know this is an old post but I have an 2011 345 RET and we love it so far.We have camped in 95*+ heat and had no problems cooling. We did get the second A/C which make a world of difference.We have also camped in 50* and the heat would run you out if need be.We didn't even turn the fire place on.
Mine has a by-pass and winterize valve in the basement storeage where the water hook up and dump valves are.
I have only used antifreeze one year and it messed up my cheep pump on my first TT so all I do is drain all tanks ,water heater, and blow air through the water system to get the water out. Pour a glass of antifreeze down all the drains to keep the traps from freezing. I have never had a problem yet going on 6 years.Our winters sometimes get in the lower teens and sometimes 0 with -0 windchills.