Well I don't just change out of a dry diaper for no reason. Being incontinent I do use my diapers as much as they can hold, but within reason and seldom ever to their max.
I always try to change right before I think they will leak. This might mean an hour early if I'm going to run an errand, or even four hours early if I'm going to bed but only moderately wet.
Either way, when I change they are almost never completely soaked, usually more like half or two-thirds soaked since this is when the chance for leaks goes up too high.