While it is true they often leak, a lot of it stems from poor owner maintenance or poor initial build quality. I check my seals twice a year and reseal around the marker lights / front window every 2 or 3 years. My 1994 Minnie has never (knock on wood) leaked and I rarely cover it (We tend to use it year-round). Just wash it, keep it clean, and reseal when needed.
Also important is using the proper sealant. On mine I need to use 311 sealant, it is what they used from the factory. Dicor will not stick to this silicone based sealant. Some people use plain silicone, or just an incompatible sealant with what is currently on their RV. Then they forget about it and it leaks...
