I like it. Screensavers but for printers. After all, the original purpose of a screensaver is to preserve the output device's health when the system is idle.

If it were built-in, you could even minimize the wasted ink and paper. Just print a single line every few days or something and keep the same sheet of paper in place for weeks or months and add to it instead of using a new sheet of paper. The ink has plenty of time to dry, so you can probably print over the same areas repeatedly.

Alternatively, you could implement it in the driver, but there's more opportunity for things to go wrong if you restart the computer, lose the connection, or have multiple computers sharing a printer.