A couple of years ago, I was looking into Swanstone. A couple of installers told me they no longer install Swanstone. They said the seams were failing a lot and it was 'costing' them too much to fix.
After contacting Swanstone, they told me that the reason the seams were failing was because they were installing 1/4" thick tops, and they need to install 1/2" tops. A 'thin' top will put stress on the seams from use and abuse. By installing a thicker top, they said the seams aren't a problem any more.
Soooo, make sure you're looking at 1/2" Swanstone and not 1/4" Swanstone for your install. And tell the contractor you 'heard' the seams were failing a lot back in the early to mid '90s. See what he says. My best to ya and hope this helps.
PS: My wife didn't want Swanstone; she got her Formica. (When she's happy, I'm happy!)