Hi,
I doubt if you take a new 10/22 w/ the plastic trigger housing and start shooting it as much as possible that you'd be able to wear out that housing.
But IME plastic's weakness lies in the fact it dries out and becomes brittle over time. Then, one day, it cracks or breaks. How long will that take? I duuno. I have faith a new plastic housing will probably outlast me at this date, but judging by the "aged" condition of a 30 yr old plastic trigger housing on a Mossberg 500 compared to the "like new" condition of an aluminum housing on a 35 yr old Remington 870 that's been shot FAR more, I'd have far less of that faith were I 20 again.
Rick C