Cartridge valve life?

Iam going to refill my current clear resin cartridge with clear resin do i have To replace the valve at the bottom ?

Typically the bite valve will last around 2-3 liters I think.

What material is the bite valve made out of?

Probably NBR or any other basic rubber.

I doubt the bite valves can be bought separately; but if I’m wrong, please post a link as to where one can buy them.

Not from FL, but they are fairly common, so I imagine just find a good size match.