Doug Miller wrote:

There's a problem in general with almost all gadgets that are intended to make
painting faster: they're speeding up the wrong part of the process. _By_far_
the most time-consuming aspect of doing a proper paint job is the prep work:
patching, washing, scraping, sanding, masking, etc. The actual application of
the paint goes quickly by comparison.

If you have a large flat area (like priming drywall in a house or
painting all the ceilings one color), an 18 inch roller will really
speed up the painting process.