To be honest, if you want a camper that will last 20 years you have two options. Buy something from about 1996 - 2005ish, do a little maintenance and then take care of it. Or, buy a new camper of any brand, remove all the windows and reseal, remove all the corner trim and reseal, remove any roof penetration and reseal, then keep up with the maintenance. They have just started making them with so many corners cut to reduce cost including quality of labor that nothing is well sealed today as you have already partly found out.
That said, if I wanted to buy new, go with a Bigfoot or Northernlite. However, I will continue to buy used with care even though I can afford new and replace each 10+ years as needed. I paid $5k for a used unit 8 years ago and it'll give me at least another 3 until I want to go a bit larger for full timing. And when I sell it, I'll probably get $5k for it with only a few hundred invested in minor repairs.
