One of mine lasted 20 years

I don’t know, but it’s amortised over the life of the machine so surely pretty low. Dishwashers last quite a while

Hand washing uses more water than dishwashers

A lot of water and machinery is used in paper production. I’d bet the dishwasher beats any compostable on water usage amortised over its 15 year life, presuming it’s usually run pretty full