You can still get new fridges that will last for decades. It just won't be one with LCD screens, ice machines, in door dispensers, complex internal designs, etc. Every one of those things simply creates a cascade of new points of failure, and component materials of varying ability to deal with the stress of being a fridge. You can buy new, efficient, fridges that are nothing but a box that cools, and a box that freezes, with doors. They will last for decades if you don't do anything crazy, or your house isn't destroyed by a natural disaster.

Depends on how old it is. Mine's a 1995 model. I've measured its energy usage and a new fridge would pay for itself at around 9-10 years if I bought a basic model*. That's around the lifespan I'd expect from a new fridge. So I'll just keep using the old one until it dies.

(*) Current fridge is a basic, low end model, so assuming I replace with a similar basic, lower end model. Payback would be much longer if I upgraded.

You still can buy modern compressor