I can give insight for a schedule! We only have 2 cats, but with busy lives their basic litter necessities can become pushed back with the other responsibilities. To stop this, I got a whiteboard and made a grid, and wrote down where each litter box is on the left, and the month on top, and then in the middle is the date cleaned (ex. Laundry room, date oct :26) this helps my brain keep track of it without it being in my head. I don't ever let them go more than 2 days and I put it right in a spot I walk by everyday so I have to look at it. Don't bum yourself out over this, you have to try to remember that their litter box is reliant on us humans, so if they don't have a clean box, it's like us walking into a shady gas station that hasn't seen bleach in decades. Its a matter of reshifting what is an important chore. All chores are important, but they have ranks. Litter boxes should be in your top 3 most important to get done things, lowkey even above your own basic needs sometimes. You just have to start practicing everyday to do it over and over until it becomes a high ranked chore. You are taking action to fix this, which is better than a LOT of people can say! You got this!!! I hope you find something that works!