Yes, aging liners are not the issue, it's the amount of time and number of wheel rotations the tube has contacted the liner. When I use Tuffy liners, I might go a year between flats, and more than once that flat was caused by the edge of the liner eventually wearing through the tube. (Don't try to patch a tube like that, just replace it.)

I tried a different brand of liner once and it ate through a tube in a matter of days. Not all liners are created equal.

If you can afford high quality tires like Gatorskins, that's probably the best way to go. My wife and I recently hit a patch of goatheads. There was one Gatorskin tire between our two bikes, and that was the only tire that survived. I don't mind changing flats, so it's hard to justify $50 per tire, but that event was illuminating.