It's a mistake to consider all campers to be the same. I don't agree they are designed to leak.
My TC is going on 12 years with no leaks and no damage. I touch up caulking from time to time and my TC is stored outside. That being said, RVs vary even within brand. If your TC is 5 years old and hasn't had issues, my guess is you don't have a bad one.
One thing to consider is old caulk is better than new caulk done the wrong way. There are people here who recaulk every year. Is it unnecessary ... that's hard to say. It works for them.