i use them on all my bikes. ride about 7-8000 mi per year. still get flats from time to time. some of them may even be CAUSED by the liners. it doesn't make any differerence because i get about twice as many without them. i use Tuffy Ultra lites. i wouldn't be surprised if the regular Tuffys provided more protection.

i can run the tires down to the casings without worry and without compromising protection. or so it seems. i run really thin and light tires, like 160-200 gram light.

there's a learning curve when replacing the liners after fixing a flat, but you'll learn...