How do you stop the seams from pulling apart in the cold? Read a forum post about how vinyl moves with the weather. They said proper post setting locks everything in place. Your zero gap install must have nailed that part. That kind of care is what makes a fence last for years.
The zero gap thing is actually for looks, it doesn't lock the panels. Vinyl needs room to move or it will buckle in summer heat. I mean, the posts are set deep for structure, but the panels should have a small gap at the rail ends. Maybe it's just me but I've seen a few push together in winter and then bulge out when it gets hot.