Bakers Pride Stone Oven

So back in 2013 I spent almost $2k converting my bottom oven from a mercury thermocouple new burners and all and it went out last week. Had a new thermalcouple installed that did solve the problem. So called bakers pride and found out that the valve has to be replaced, that since they had to switch from mercury to new the valves are not lasting as long. My tech guy said he has been replacing them like candy over the last yr or so.

Why can’t bakers pride make the valves correctly so they will last longer than a few yrs