The switches eventually fail, but most mice use the same Omron switches and they are easy enough to replace if you know how to solder. The teflon skates wear out too, but you can find replacement for most name brand mice online.

I've had buttons stop working. The mechanism inside that registers the click is a mechanical switch and they eventually die

Or when their old mouse is grody

That's planned obsolescence. They cover the mouse in soft touch plastic that turns to glue in 5 years. It ensures that you buy a new mouse every 5 years while claiming they are reliable.

I read that acetone transforms the gluely soft touch coating to hard plastic. I did it to my old Logitech when it got grody and it is still not grody after 20 years.

I had the wheel button stop working on it once, it was still usable, just annoying, when I needed to do a middle click.

Also that happened after a decade of use.

By "forever" they mean you will be paying them forever for the privilege of using the mouse. Unless you break it that is, or they feel like they no longer want to support it at which point it will likely become a forever brick.

Yes, mice are forever mice. That’s the problem, it’s just a one time sell.

Ask a razer user if their mouse/keyboard last forever.