Is There A Half-Life For Coins In Circulation?

Yep, me too (General Chemistry and Introductory Organic/Biochem). Double the work right now since I am doing video-conference style lectures, but I also need to post a lot of extra materials for students who don't have the bandwidth to dial in (it's an inner city school). Spent the last day before lock-down photographing steps in some labs so we can do them in "virtual" fashion.
Still haven't figured out how I'll do exams.

Personally, I cannot walk past a penny without picking it up. I guess I am helping the economy by returning it to the mix.

I admit, however, that I do not recycle really, really pitifully damaged pennies. I usually hoard them until I have a dozen or so and then trash them.