Some years back, my employer's HP all-in-one decided to expire the printhead. WTF? I could see throwing a warning if a clog were detected, but no, this was time-based. I'd never heard of any rational reason beyond clogs to replace a printhead, and if it's replaceable, it ought to be cleanable.

The punch line: that POS wouldn't even let me scan with the "expired" printhead in place.

HP: Never Again.