The problem I see is that a static test tells you little. The material the belt is made of gradually deteriorates and when it's needed is when it's most likely to fail.

Maybe you can get them rewebbed, then you's be good to go. But in today's litigious society who does that anymore? I remember some time back a lawyer type got on here trying to get the collective to ID some 30 year old flex fan that had failed and threw a blade. The consensus was "it's 30 years old, subjected to who knows what damage over the years, go away". I don't think he ever got an ID.