Seasonal lot is the way to go. Set it up once, and then its there. I dont think the mindset that you will put your trailer on a lot and then not use it is is very valid, no more so then folks who leave the trailer in their yard and never go out. Lets face it, the few hours it takes to setup is a PITB in my opinion. Not to mention your putting wear and tear on your vehicle and trailer. Oh and the price of gas, atleast up here in northern alberta at 1.25/litre is easily recouped by having the trailer parked on a seasonal lot. My 2500HD doesnt exactly get good gas mileage.
In terms of buying new, we bought our 31' KZ travel trailer in 2011 brand new. However our house did burn in a wildfire and we needed something to live in from May - October. We had a lot at an RV park for that first summer, and It was ok, considering the circumstances. Last summer i towed it all over, and 2 things happened. 1) I destroyed my half ton and had to buy a 3/4 ton, and 2) I sure missed not having to set it up and pack it up every trip.
A seasonal lot became available 85km from home, and our camper is there, and will be there for as long as that camp ground is in business. So awesome.