I like your solution, keeping it simple is always the best. If I was concerned about wear I would be more worried about it in the housing than in the metal of the micro switch arm.
When I copy your idea, I might move the switch back a bit so that less of the arm is in contact with the filament and possibly also extend the PTFE tube inside the housing and cut a slot into it for the micro switch arm. Both of these mods should reduce friction.
