What part is failing? Is the magnetic coil failing? Or is the relay not switching between sets of contacts?
If its the coil, about the only thing you can do is to check if the actuation voltage is within the coil specification. Barring that, it may just be bad luck or a bad design or faulty manufacturing from the factory. Suburban once had a problem like that with water heater circuit boards. If that's the case, I would be looking for an equivalent relay from another manufacturer.
If it's a problem with the contacts welding together, it's usually a result of arcing when making or breaking contact. HERE
is an article on arc suppression if you are interested. Otherwise, the only way to deal with arching is to reduce the load being switched. Or you could file the contacts periodically to smoothe them out again.