All my print heads are out of warranty but still going strong but eventually I may want to change them.
Just wondered if shelving a new print head is a good idea so it's ready to use if needed.
I have heard the print heads have an expiry date just like ink cartridges is that true?
They have an 'expiration date' in that the HP print utility will note that they are 'out of warranty', but they continue to work just fine. I'm still on the original print heads at 5 out of 6 positions on my Z3100 after nearly two years of use. When I had one print head damaged through my own stupidity (running thick paper through the machine with a thin paper preset), HP shipped me a replacement by next-day air.
I would only bother having spare print heads on the shelf if you're printing a lot of commercial work and can't afford to be down the one or two days it takes to get a replacement.