Punctures for cyclists tend to come in threes, sods law or whatever you call it, it does seem to be the case.
They also happen when you are 20 miles out, not always the case.
They happen when it is pouring down or at other inconvenient times.
Canal tow paths are notorious - they do not clear up those thorns.
After a recent visit to the Loire and picking up our 3rd puncture I resorted to twitter and Bob Clewley and Phil at Izzyminx recommended Slime Tube Sealant, on the basis that prevention was better than cure.
A can will retail at about £10,though they are available on the internet for less and they will do a couple of tyres.
You remove the valve insert so ok to use on Schrader valves (car type valves) but no use on presta valves. You then fill the inner tubes with the gunge and then inflate your tyres.
The principle is simple, when you get a puncture the slime seeps into the hole and seals it. You need to keep your tyres fully inflated for two reasons, firstly to push the slime into the hole and secondly you will lose some pressure with the puncture. In any case you should keep your tyres inflated and also check them regularly for nasties.
It is also possible to buy slime filled inner tubes.
The manufactures claim that it lasts for two years.
It will only cover small punctures such as from thorns on towpaths and pins and will do nothing for tyre wall splits or pinch punctures as a result of hitting something hard at speed, but that is really not often a problem for us on our sedate travels.
You can also use the product to deal with a puncture so carrying a can is an option.
An alternative product is one that seals and inflates but if you are not careful you can become somewhat over loaded. Spare wheel anyone?
So perhaps prevention is better than cure.
If you want to get fanatical about preventing punctures you could consider Kevlar belted tyres or other so called puncture resistant tyres. Though some claim that the keflar tyres are effective against the blunt objects but not against thorns. You could get inserts that go between the tyre and inner tube that act as a protective barrier.
Alternatively you can carry a puncture repair kit and some spare inner tubes and in any case repairing a puncture at the roadside sorts out the amateurs from the professionals. Also it allows you to benefit from the camaraderie of the track, the opportunity to help or be helped.
In any case there will always be something else that can happen and you can not cover every eventuality. I lost a derailleur gear hanger 20 miles out on the Canal du Midi from a stone getting jammed in it, a once in a blue moon event, my cycle repair shop had never come across it before.
Bottom line is you pay your money and take your choice.