Replace Printhead Based Upon Expiration Date
HP plotter printheads usually have an expiration date printed on the head. Typically this date is either one year, one-and-a-half years or two years from the manufactured date, depending on your plotter model. If the printhead is used past this date, HP does not guarantee the print quality.
Replace Printhead Based Upon Ink Use
When an HP plotter printhead has reached an ink use of more than 1,000 milliliters, it is considered to be expired. HP does not guarantee the print quality. However, it does depend on your plotter model.
When deciding when to replace the printhead on your HP plotter, you can use the given expiration date or you can monitor your ink use. Both are suggested ways to make a feasible determination. However, both of these options have one additional determining factor that really makes both of them null and void, and that is the actual print quality. If the print quality remains suitable for your needs after the expiration date or ink usage limit is exceeded, you should continue to use it. However, if the print quality is less than desirable, you should definitely replace it. Print quality is what matters most.