I'm trying to create a formula checkbox field with a if statement that stops once the checkbox is checked. I have data that is constantly changing so the statement might be true one day and not true the next, but I want the formula to stop computing once the statement is true.
the first condition is not met the second condition is met, so the checkbox is checked and it stops there - the third condition is not evaluated
So if you want your formula to stop working once the checkbox is checked, order your conditions such that all the cases in which it's checked are evaluated first, and once a condition to check the checkbox is satisfied, your formula has done its job and will stop.
Another thing you might consider is to use an automation instead of a formula. Set the conditions for when you want it checked in the Trigger. When those are met the first time then have it check your box.