I did my fluorescents twice.
First time with the cheapest chinese ones I could find on ebay. These did not last. Same as said above, after even a short time, the chips were failing, dimming and going out completely.
Second time around I did more research and spent a lil more money.
I still bought Hong Kong from ebay, but was careful to look for ones that listed a wide voltage range. These have built in regulators, and can better take the RV's electricity. Normally bright down below 10 volts, and won't be damaged at 20.
The second time, I also did not get ones listed as waterproof. The waterproof ones have a thick clear rubbery coating. My first batch got hot, thinking the covering (and sealing them inside the fixtures) contributed to the failures.
The second set has worked perfectly and lasted 4 years and counting.