Check out a thread titled: “Treatment of Slightly Oxidized Fiberglass”. There are several posts addressing preferred products. The consensus favors the Maguire line of fiberglass products. However, I went to West Marine for advice, and the staff told me that 3M was just as good. This thread also describes the 3 step process involved in deoxidizing & polishing the fiberglass outer shell. Because you have a new trailer, the Maguire 3-step kit will work very well for you. I add a 4th step and use a finishing polish to bring out a shine.
In answer to your question, in 10years, your Oliver’s fiberglass exterior should look just like new “if well maintained”. Let me be the first to suggest, “if well maintained.” requires a fair amount of discipline, elbow grease & consistency.
The first thing you need to do is keep your Oliver
out of direct sunlight when you are not camping. To do this, you need a secure structure to park it under, or a canvas cover. If you use a canvas cover, make sure the fiberglass skin is clean and dry. Otherwise, the dirt on the fiberglass will rub against the cover and the scratch the gel coat.
Even if you don’t use a canvas cover, you should wash your camper upon returning home from camping trips. I use 22 Mule Team Borax mixed with a pale of water.
Every 6-8 months, you should de oxidize and polish your trailer. As rainy season approaches it’s also a good idea to spray the fiberglass with a moss protective product. Be sure to spray all the nooks & crannies.
Life is short, and for a price you can find someone who works with fiberglass boats or trailers to do the grunt work and climb up ladders tall enough to work on your roof.
If you can do all that, you’ll have a lasting gel coat.