There are extra thick tubes ("thorn proof", yea...) in some common sizes. Usually the extra wall thickness is focused on the outer tread portion. usually the resulting ride quality suffers (weight goes up and suppleness goes down).

There are goop filled tubes that will try to self seal some cuts. Works to a degree on some punctures and in time usually plugs the valve (Slime can't tell the difference between a puncture and the valve). Most solutions only claim a year of function at best.

Usually the more you ride the fewer flats per mile you'll get. Why? Well you'll learn to take better care of a few things. Where on the road you place your tires. Pressure maintenance. Tire and rim strip replacement maintenance. You'll learn which tires and widths work better for you (wider are more robust and offer more traction). You'll learn to check the tire's tread section for bits imbedded and remove them before they fully penetrate through. You'll learn to brush off the tire treads sections after riding through glass patches.

Still with all this there will be mystery flats. No found penetration or cuts from wiggled out flakes. No cut casings or rim strips. Valve bases can give out (often from low pressure riding). Tube can be abraded by the casing inside surface (low tire pressure again). New wheels can have metal shavings trapped by the rim tape that can move around and get at the tube. Valves can get a scored seat then leak.

At one flat for 400 miles the op is not out of the ordinary. I get about one flat every 1000+- miles. The best years are about one for 3000 miles. The worst are three in one day.

Today I repaired 5 flats at work. Only one was a fleck of glass. Another was a side wall cut aneurysm. Another was internal abrasion. Another a valve base tear. The last one I was a pinch flat.

Like so many issues with riding the solutions are more with the rider and less with the equipment. Andy.