I'll say again, I am a huge fan of tire liners (Mister Tuffy and Rhinodillo are well-known brands). But with a few caveats.
The sharp edge at the ends of the tire liner can actually cut your tube. Less likely but still possible is that the tube will be pinched between the tire and the edge of the tire liner. Both of these will cause flats in short order. As the tire liner ages it can dry out and crack, also produces sharp edges that can cut your tube.
The upshot of this is that (1) you need to be damned careful installing tire liners (and might just want to pay your bike shop to do it), and (2) once a year you ought to remove your tires and inspect your tire liners, and replace them if they are starting to show cracks.