They are humungously big and heavy aren't they? I see quite a few being sold on, tells a story..... Performance-wise, with a big fan pointed straight down at the carpet you'll get a circle about 6ft diameter bone dry in that time but as you get further out from the radius of the fan it'll be less and less dry... obvious really!!
Far better to spread air flow over the surface and get all of it a bit drier, rather than a dry circle in the middle of a carpet that's mostly still wet. Also it will really only be effective in an empty room, as furniture will disturb the air flow.
When drying's an issue I use 1 or 2 air movers depending on how many rooms, I put one on the carpet straight away after the first section is extracted and just work them back so each bit get a blast. If cleaning a whole house I'll have one upstairs and one downstairs, can normally get most of the carpets touch dry or near enough without sitting twiddling thumbs afterwards.