I have a approx. 8 years old Brother HL5150D, a b/w laser printer with duplex unit at home. The older the printer got, the longer a print was lasting using Ubuntu Linux and either the original Brother PPD or the Openprinting PPD; of course both for CUPS and Linux. And I tried a whole lot of other printer drivers as well.
Then I was evaluating a new printer for home use, nowadays a color laser MFC with duplex unit, where there are not that many of them for rather budget price. And the biggest point was Linux compatibility. While googling, I stumbled over a message, that (at least for Canon printers), Gutenprint drivers are a lot better working than the original ones, if there were.
So I give it a shot and tried the Gutenprint driver for my old Brother. Astonishingly, even with full graphic pages, printing a duplex page lasted less than half a minute (while before, print preparation and data transmission lasted much more than 5 minutes per duplex page). I tried with many different PDF and image files, the paper came out of the printer very fast and reliable.
So do I really need a new printer now? Having colored prints is a temptation. But pure technical speaking, I don’t need a new printer now.