To answer your question...yes the fins become brittle over time. Where I live on the coast they will fall / flake off, especially on the older a/c units ( not necessarily just RV ). I have seen window units where you can just touch the fins and they fall off. Not much you can do but keep it rinsed or use the coil cleaner. The newer units have better corrosion resistance. Unless it is totally clogged it should be ok for a while. I would run it till it dies. I have a similar problem on a mobile home rental. Works fine now but if it quits I will not even consider repair, just replace it.
