I haven't owned a fiberglass sided RV yet, but that will likely change with my next one. The aluminum siding on my 2004 trailer has held up well except as pointed out that it is susceptible to dents and punctures. I've used aluminum tape on a couple stab wounds from branches. My trailer lives outside year round and sealing the windows and edges has not been a burden. I did it once when the trailer was new, then again after about 5 years. The decals are peeling here and there, and the door is a little yellowed, but overall it's sound. Now, in its 18th year, It needs it again around the front running lights, but the rest still looks pretty good. I expect with a little TLC, a fiberglass RV would perform similarly. I believe the key is immediate preventive maintenance upon purchase. JMHO
