I very seldom empty out the cat boxes completely - maybe every few months. I have three for three kitties. I just keep replacing the Fresh Step. I do not think there is any odor and my skinkids also tell me this when they come to visit. I am pretty neurotic about cleaning and odors! I scoop the box at least 2-3 times a day and I know hubby scoops also. When I do a complete cleaning, I will scrub the boxes and swish them with bleach, rinse like crazy and then refill them - but again - very rarely. I think the Fresh Step keeps them as clean as can be! Also, I keep them pretty full so that urine never does reach the bottom of the box so that probably helps also.