I'm just concerned about Hot tub being outside on the deck. Rodents and bugs due much damage?
Most of the better brands of spas are pretty critter-proof. About the only ones that have trouble are the "kit" spas that are sold on the side of the road and out of storage facilities:
Varmints love to get inside a hollow cabinet and chew on the plumbing when they get the fidgets.
The other concern is filters. The envoy has 5 of them! So thats $150 plus filter change.
The Envoy has 5 Tri-X filters which are rated to last 7-10 years. They cost around $60/each and can be cleaned in the dishwasher. A great many of my customers have switched to them and are tickled pink with the results.
What cold weather problems could I expect? Freezing on panel controls or the like?
I can't speak for other brands, but that has not ever been a concern on a HotSpring Spa. HotSpring has dealers in Switzerland, Greenland, the Netherlands, and some other mighty cold places. They are built like a tank and can take pretty much any condition Mammy Nature hurls at them.
Brer Terminator