The gruelingly-slow pace by which Fray (whatever it is) progresses across the patch of carpet where the novel takes place indicates that the Carpet People live out their lives at a much faster rate than we humans, or even than the nomes from The Bromeliad Trilogy. That's consistent with the author's other works; the latter story also presupposes that smaller beings in Sir Pterry's worlds experience time at a more rapid pace than large ones, and Reaper Man likewise explores this concept with its glimpses of tree and mayfly life.
However, it's not consistent with how the Carpet-dwellers evidently experience a regular cycle of days and nights, which seem not that different in duration to them from how our own world's feel to us. How can this be, if it takes so many, many of those tiny peoples' "days" for a human to tread/sweep/vacuum/whatever a short stretch of floor covering? Simple: the periods of light and dark which the Carpet experiences are (from our perspective) the near-instantaneous flickers of brightness and shadow that fall upon its surface, as the room's ceiling lamp shines through the vanes of a rotary fan. Its rotation, too fast for us to even see, is slow enough to such miniscule beings that it takes all night for a vane to pass overhead, and all day for the next to appear above them. No Munrung, Dumii, Deftmene, or wight living has actually witnessed a human-scale day/night transition, and any Carpet-dweller who's alive to seen the room's lamp switched off for the evening will be in for one heck of a surprise.
