I have never once heard of a surgeon or cardiologist telling someone to expect a mechanical valve to last 15-20 years. That is not supported by the data at all
September 2020, had a telemedicine appointment/consult with a surgeon at Providence St.Vincent. I didn't know a whole lot at the time as the diagnosis was still fresh. After going over the condition he talked a bit about bio valves, then talked about mechanical valves.
He stated "let me tell you a secret, mechanical valves don't last forever either, 15-20 years on average. My plan for you would be put in a mech valve and when that valve needs to be changed go with bio.". Then went on to talk about some patients he knows about that maintain their valves only on aspirin etc... Then proceeded to tell me I needed surgery right away.
I agree, it's very bizarre statement, not sure why cardiology is so full of contradictions when it's so often presented as a simple plumbing problem. But maybe it's just me, other people don't seem to run into these situations.