;-)
thank you.
is it possible that after protecting against a few transients the transorb will stay "open" and not provide any protection and i will not know?
You are referring to transsorb diodes (power Z-diodes)? They can be generally expected to fail short circuit, at least in a medium transient energy range. But supplying unlimited current to the device can of course cause an open circuit or even melting/evaporation of the connecting PCB traces. You most likely will know about the event (smell and hear it).
It is possible, but unlikely. The amount of energy it takes to open the device usually blows it wide open physically and the smoke escapes. Everyone knows that electronic devices can't operate correctly without magic smoke.