I went to school with a guy named Kenny K., he had a KZ200. It was up on the centerstand, idling in gear while he cleaned the chain with a rag. A KZ200 has no torque. His fingers stalled the engine. It took the fire department to get him out. This was in 78 or so. I don't recall if he lost fingers, or if they were just pointed in different directions after he did it. Kenny, are you reading this?
Back to chain durability and life. I've found that if you use the highest quality chain, you will have no issues. And to me, the highest quality (and most expensive) chain is the DID ZVM. I use them exclusively, my KTM has the nickel plated one, my Ducati has the gold one. And a steel, or steel over aluminum sprocket. And I use factory made or sold fronts. No issues. The Ducati went 20,000 plus miles, I happened to have a spare set so I replaced them. The KTM chain was getting kind of hinky at 10,000, I put the nickel DID on just for peace of mind.
I use WD40 to clean them off, some old wives tales about WD eating the orings seems to be false, I've never had a problem. What will kill that chain is dirt grinding things up. I'd suggest carrying WD and cleaning that sucker whenever it gets coated with grit. What else can you do? Don't use pressure washers on them, it will force water past the orings. Keep it as clean as you can, you should be good to go. As long as your points and Amal carburetors don't give you issues (inside joke, sort of.).