I dont know what is standard, but when we bought our Grand Design Momentum TH, they specified that the warranty covered full-time living. In 2014 we did not see that published with very many manufacturers. The reality is that there seems to be very little difference in the way 5vers are manufactured, but what is different is their service after the sale. I'm speaking of the manufacturer - not the dealer. Dealers could generally care less unless they see another purchase in the immediate future.
With that said, unless a warranty specifically stated that I did NOT cover full-time use, I think any manufacturer would have problems denying coverage.