We average 50 - 75 students per quarter.4 quarters per year. So between 200 and 300 students per year. All the newbies start in gas welding , and then migrate to the Handlers for their first arc welds.
These are my best guesses after teaching at SSCC for 6 years.
Gun liners last about 18 months. Triggers last about 2-3 years. Gun cable about 4 years. Diodes about 7-8 years. Capacitors about 6-10 years. Main contactor relay 6-8 years Gas Solenoid 7-9 years Nozzles about 6 months. Gas diffusers about 1 year.
So far we have yet to have a wire feed motor go out, and only a few have blown their caps or diodes. We have a high attrition on gun cables because the students tend to abuse them, out of ignorance, not by intent. Coiling them too tight, pulling the machine around by the gun, dropping the gun on the concrete, clogging the nozzle and diffuser with spatter, it all adds up. I would guess we get about 10 times the wear on our 110 volt MIGs as compared to a privately owned one. I am amazed how well they have held up. t this point the gun parts are getting more expensive, they are made by OXO, but those guns are no longer OEM on any current machines.
Miller switched all of their machines and all of the Hobart machines to Tregaskis guns, so those parts are cheaper and easier to get now
Personally I think the OXO guns are much better than the lighter duty Tregaskis guns, which is funny since both companies are owned by Miller's parent company, ITW.
M personal Handler 120 has lasted 10 years. I have replaced: Main contactor once, fan motor once, gas solenoid once, gun liner 3 times, trigger twice. Mine has seen much harder use than most hobbiests will put theirs through.
If you want your diodes to last, never pull the trigger to burn off a wire that stubs into a cooling weld. Just wiggle the gun to break the wire off or clip it with snips. If you do pull the trigger to burn the wire off you dead short the diodes, which is not kind and will kill them quicker than anything else. This tidbit is from both welding repair guys I know.