There are SSR solid state relays which is a semiconductor relay, these will not pit.
One just have to check which one to get, what voltage to switch them and so on.
But when that is said, you really have to check that there is no short or anything else creating these failures.
Which in turn may solve your problem all together.
To me this relay seem quite flimsy, are you sure it is rated for the amount of current your kiln are drawing?
Regards Per-Ove
Edit to add:
You should also check that the 12v dc transformer gives stable voltage and not fluctuating, creating a “vibrating” on/off condition.
This will burn out your contacts quite fast.
In worst case they can melt the contacts together locking the elements in on position.