I conduct lab experiments over a zoom call to students, which demonstrates certain principles in physics.
I have to purchase certain things like screws, bolts, batteries, small motors etc. Nothing too expensive. Most of this stuff breaks in a few days, so definitely less than 2 year life span.
As these are directly related to the service you are selling, I would say they are cost of sales, not overheads (which are more the admin-type costs of running a business). Exactly where you classify them is up to you but general purchase sounds fine.