Getting ready for camping season

I may be naive, but how can I determine if an exterior seam is in need of resealing? What does a previously sealed seam look like if it is in danger of leaking? I have an early 2016 Pod 179, and it has been stored for one winter uncovered and one winter covered with a cover made for a 179. In western Oregon we have moisture, but we are not subject to the extremes of heat or cold that other areas or states experience. Would the western Oregon climate not cause the need for resealing perhaps because the more mild climate doesn't cause cracks to develop? I just don't know what it looks like if it needs resealing. There have been no leaks inside to date. We've had it out several times in 2016 and 2017, but don't want to take a chance on leaks developing in 2018. Any ideas that will help me keep the Pod as clean and available as possible?