I had a few leak problems when I first got mine. The problem was address in Ohio when we went to NY, But we had about 5" of rain in Ill. But a leak showed up again later when we got back to CA. Took it to Custom RV and they worked on it. So far so good. But I do think the factory went to work on the problem and I don't think I have read anymore about leaks. As far as how often should you replace caulk who knows.
As far as walking on the roof. I don't (182 LBS) but my wife does (130 Lbs) she washes it with Wash and Wax All. And she will do this for me once a month.
