My partner let me take her 10-year-old MacBook Air after getting a newer laptop for herself. I’ve refurbished it for some basic use (email, web browsing, conference calls, writing/development) by installing a new battery and SSD.
I admit some of the decision to do this was idle curiosity. My eight-year-old personal laptop, a 15" Retina MacBook Pro, doesn’t have a battery that’s easily user-replaceable without using solvents, so it’s nice to have a lightweight secondary machine that now has over eight hours of battery life under light usage.
I also admit I had the desire to reduce e-waste, so Kris De Decker’s Low Tech Magazine article on avoiding buying new laptops also inspired me. I’m curious to see how usable Mac OS 10.15 will be before I possibly partition the drive and install Linux to be able to dual-boot the machine.