The great thing about Coleman is they are completely rebuildable! Do a little google based on the model number of your stoves. Typically two things go bad on these, the pump or the generator. If you can pump up the fuel tank and it builds pressure then the pump is good. If the thing coughs and sputters trying to light then replace the generator all with simple hand tools.
When I bought my stove it ran rough but instead of replacing the generator, I mixed Chevron Techron fuel treatment in with the fuel and ran about a 1/4 tank through it and it straightened it right up. It just builds up like a regular carburetor. Unless the end is damaged in some way I wouldn't think it would be a wear item. A new cap gasket and valve packing and it was back in business.