Youd be suprised how long RTV can last/go. I drilled a hole and mounted a bracket to the front of a semi truck (warning lights). Used rtv to seal it up to prevent leaks, 1 million miles later still not a single leak from it. This was exposed to direct sun, wind, rain, snow, extreme cold (it routinely went to canada and the mid west in winter) and extreme heat. I checked everytime it came in/back and never a leak. Just saying.
All that said, I like RTV because I can easily replace it if something goes wrong.