I will admit right off the bat that probably we're not doing all the litterbox cleaning that we should.
We have one cat. Her litterbox is in a room at the top of the stairs on the second floor. Now that the weather is colder, we're keeping windows shut...and when I walk into our house from outside I'm immediately hit with that ammonia-y litterbox smell (only poop smells when she's just recently pooped).
We use World's Best litter. We scoop out the poop and pee clumps about every two to seven days ...although recently I've been trying to do it every 1-2 days. We never really empty out the whole box and wash it out. When we add fresh litter, which is usually only every few weeks, the smell is less noticable for a couple days. What I'm doing now is opening the window in the litterbox room and turning on a window fan so that it's blowing out. This helps, but is not something we can keep doing since it's almost winter.
Suggestions (criticisms!) please!!