I have a 2 year old unit that requires $1250 worth of work to replace a faulty expansion valve. The service tech made it clear that this part was a problem and was replaced by Lennox in other models. Is there a way to find out when this part became an issue?

I would advise you to get a second opinion, that price is way out of line for replacing a txv or even the entire evaporator coil. Good luck . Mike