The inner thigh seams WILL wear out, mine took about a year. It's a common complaint I've heard about the tights. They are wonderful though.
For those Seattle folks (Knot), I know a seamstress who will fix them when it happens. It's better if you catch them before they start to fail and it isn't perfect. If it goes when you're out for a long run, OUCH.
FYI the weather tights (can't remember the name offhand) are really warm and they repel snow/rain wonderfully. It has to be 20ish before I'll wear them or else I'll get too hot.