We have been fulltime for 1 1/2 years in a 2011 Carriage Cameo. Love the trailer. We have spent the last 2 winters in AZ/CA. We have had some cold snowy weather in the spring after getting back to Canada & in the fall before heading south. The trailer handled the weather well. As long as we kept the furnace on - no problems with water lines.
Whatever you get, we HIGHLY recommend dual pane windows.
Being from Canada, you might also want to check out Triple E Topaz. Triple E isn't currently building 5th wheels (only motorhomes) but they are a very well built trailer if you can find one that suits you.
Arctic Fox is also a good option. We have 2 friends that have AF & they are very happy with them.