You can never clean the carpet well enough around a litter box. Even if you have a cat that is nice and keeps things inside it. Even if you make it point to get the good vacuum out for it. Just put down rubber mats or a shower curtain or something easier to clean than fabric.
We were thinking about getting the carpets cleaned anyway, but now I'm thinking the cleaning is really just to give us time to save up for new flooring. This litter area was in use for the entirety of the 14 years we've lived here, and it shows (or smells, I should say).