prepare a letter during a snowie power cut
My sister took a Canon Starwriter to uni back in 1990 or so. I bet that would run for hours on a typical UPS.
I have a UPS powering my entire "office" *, including the printer, though as the printer is a Xerox solid ink Phaser, it doesn't stay up for terribly long if the printer is actually printing :-)
Why? Well, the Phaser needs to keep a reservoir of liquid ink. If the power is interrupted even for a second, the printer goes through a cleaning phase and wastes a whole load of ink. We have quite a lot of short-term power cuts where I live.
* Office consisting of two AMD-based OpenSuse machines, an Intel Mac mini, a Raspberry Pi, an Acorn RiscPC and all the associated gubbins. I have lots of children all wanting to do homework at the same time :-)