I was pondering the SoL issue after I read Law Student's post on the previous page of this thread... Then it came to me, like a loose brick from a tall building.
If they're gonna sue you, they have to sue you
where you live. As in, they have to file in a court that has jurisdiction in your state and county. That being the case, SoL is determined by that court's rules, which are dictated by your state's laws.
In other words... Say I had a debt from West Buttplugg, and that it had been 7 years since I made the last payment. The evil, nasty CA can't file suit in West Buttplugg, even if their SoL is 10 years for this type of debt, because I don't live there. For my sins, I live in Vermont, so that's where they'll have to file their case. Vermont's state laws state that the SoL is six years for most civil actions, including this type. They file, I show up and tell the judge it's time barred, case dismissed.
Clear as mud, right?