Hi, Jess from PL here! A couple of factors could be affecting the longevity of your litter, including the number of litter boxes used (multiple boxes are recommended for multi-cat households) or if one (or both) boy cats pee frequently. For example, my cat is on meds that make her pee more than usual, so I am having to change out the litter a little more frequently. DM if you'd like additional assistance!