How often to change the litter?

when it starts to smell.

I clean my cat litter tray out as soon as my cat has soiled it.

There are litter boxes that help clean themselves, so you don't have to change it so often.

I scoop till the total depth ends up getting down to 1/2 inch then empty that and refill till it's 3" deep.

I would not let even the best cat litter to go longer than a week.

Fortunately my cat prefers to do his business in the forest and rarely uses the litter dish for weeks at a time.

It really depends on the litter box. I have multiple boxes in my house. The one my cat prefers to use I completely change every 1 - 2 weeks. The one my cat doesn't normally use I completely empty after 3 - 4 weeks.

I have four cats and five boxes and use wood stove pellets (the best!!!). Poop is scooped daily and the pans are dumped out once a week.

As needed and well before it starts to stink. I no longer have any cats however I did have one for several years that passed on. I had two litter boxes that I cleaned multiple times a day, usually very soon after she used them. This kept the smell down. She kicked litter out even when I upgraded to the enclosed litter boxes when she was burying her business pies so I was cleaning up after her almost constantly.

Litter should be changed once a week in my opinion. Between an inch and a half and maybe 3 inches deep was plenty for my 1 cat, it doesn't have to be real deep just enough so they can bury the solid waste.

Every third day is best.

When I first got my cat, I scooped the litter daily and completely changed the litter box once a week. Now, with more experience, I've become more efficient.

First, this depends on how many cats you have, the litter you use, etc. This is what I do now for my (one) cat:

The first and major thing that helped was investing in a giant, high-sided litter box. The next thing is to make sure you use a good litter. Personally, I would recommend scented clumping clay litter. It's easy to clean up and keeps everything smelling fresh. I use Tidy Cats with Glade. For cleaning, I scoop every day to every other day depending on my schedule and I completely change and wipe down the litter box every two weeks. Or I just change the litter once a week and clean the box every 2 weeks.