New car manufacturers use induction hardening because everything is new and fresh. And it is fewer machining operations, and potentially more reliable. Also costs less, the all important profit...
In a automotive machine shop we aren't dealing with new stuff usually.
Usually 35 year old worn out stuff for the hot rod crowd.
So induction hardening a seat that is sunk 1/8" is not a possibility.
You have to cut the old material away, install a new seat, then cut it.
The stellite seats are harder than anything the factory does. If properly installed they are great.
10K shouldn't be a problem on even a non-hardened seat.
A little lead additive, even if not every tank will help but isn't mandatory.
Sometimes they last a long time, others they seem to go quicker..
if the guides are in good shape, they'll last probably until the motor is in need of an overhaul.