I used to sell LED's and the LED itself when properly controlled electrically will last for a generation with virtually no light loss, BUT......the electrical control circuits for LED's is the secret. Cheap and dirty = poor performance. Properly designed = MUCH more expensive.
I think a lot of the cheap LED's are just that - Cheap. The higher priced ones aren't even designed to last much longer than the incandescent or fluorescent lamps they replace. Who would want to make a product that would last a lifetime?
Will LED's save power and certainly that is important in RV's, but long life/performance? Ain't Gonna Happen! IMHO