First time trailer owner here. We have a 2013 thirty two foot Heartland Prowler and I am wondering how often or, when should I consider resealing the roof. Also, where do I find out what product/s I would need to do it? I am the third owner of this trailer and it went from the dealer to a seasonal lot where it sits today. Although I have not seen any signs of leakage, we had a lot of snow this winter so I will have to do a close inspection once we open up this season. Thanks