They are specially heat treaded, sent off from the manufacturer to do so, hence the 5 week lead time
Have heard of them wearing quickly (but none of them worn out) and also lasting 20k miles with minimal wear. I guess it depends on driving conditions, belt type, alignment and tension
Don't know how long the phase 1 lasted, maybe someone could comment
Realistically for me at 20k as a minimum, that would be 4 years of dailying of 8-10 years of my weekend toy, so plenty of wear in them compared to the cost