Those are my little fetchaholic Rory's favorite balls. I've had that problem, but she really works the squeaker when we are playing fetch. Some packs of balls last longer than others. Usually, the squeaker actually falls into the ball, so you hear it rattle around and not squeak. If I notice the squeaker starting to poke out I just toss it, and she has to suffer through fetch without any squeaking until it's time to replace that ball.
My girls are so fetch obsessed I can't just leave their balls mixed in with their toys in their toyboxes. They only get to play fetch with their balls for 30 minutes straight down our long hallway every night, so they are never really just unattended to chew on them. Poor pups have to suffer and play fetch with one of their zillion other toys during the day when the balls are up out of reach.
Fetch Maniacs - YouTube