I perform litter box duty at least twice a day, simply to keep kitty happy. Hopefully, the box is located somewhere easily accessible and within sight, possibly where you pass nearby several times a day (this serves as an easy reminder). I empty the litter (scoopable) into a small, empty, plastic bag lined trash can like the kind you would find in your bathroom. Makes easy for taking out to the trash once it starts to get too full.
Having the litter box in the bathroom might work well, unless your kitty scatters litter on to the floor (like mine does). Like another reader commented, the Arm and Hammer product works well; but for cost effectiveness, I have found that Arm and Hammer Carpet Deodorizer (there is one for Pet Odors but not necessary), works equally as well. You get more of the product for less money.
Procedure: Scoop out the litter and clear out a broad path to the bottom, then sprinkle a generous portion across the bottom of the box before putting more litter in or respreading what litter remains back over top (either way as needed). Doing this 'as a habit' should eventually remove any residual odors. Might want to see how clean the box is and maybe start out fresh with a thoroughly cleaned box (do NOT line the box with a plastic litter box liner!).
Those are a major FAIL and are messy as well a 'smelly' especially when it comes to urine.
The only downfall to this technique of adding the deodorizer might be that your kitty (kitties??!) might be offended by the smell that is so pleasant to humans. in which case, basic baking soda might do the trick, although I've never had a need to resort to it.
With the past two cats I've had over the years it has not been a problem at all. They have not be offended by the 'pleasant odor' like I've read from time to time in some 'how to' email cat care newsletters or online web sites. Stephen (and Lola)