An inkjet printer that has a printhead with an array of ejection devices for ejecting drops of liquid onto a media substrate. Each of the ejection devices having a chamber for holding liquid, a nozzle in fluid communication with the chamber and a heater positioned in the chamber for contact with the liquid such that resistive heating of the heater generates a vapor bubble that ejects a drop of the liquid through the nozzle. The printer also has a controller for receiving print data and generating drive pulses to energize the heaters in accordance with the print data. The controller increases the drive pulse energy during the printhead lifetime.