…if you have only had one puncture in 20 years then you have either been extremely lucky or have covered hardly any miles. Punctures are very rarely, if ever, caused by incorrect tyre pressure.
I used to do around 25,000-30,000 miles a year. For about 10 years I frequently had to drive around factory roads where the incidence of debris had to be seen to be believed. This is the main cause of punctures. I scrapped many tyres through large bolts etc being embedded in the side of the tread !
I have had one of the cheap Halfords-type compressors for about 10/15 years now and have used it many times for topping up but it is just not man enough to inflate a nearly flat tyre and they are only short-rated and overheat quickly. I agree, worth getting one though.
I think the jury is out on these gunk-filled canisters in place of a spare, even a space saver, - Condemn them !
Just to clear up a couple of points…
I average 12–15 thousand a year x 20 would be well over 300,000 plus travelled miles.And whilst I think that is a lot of miles to lug a never used, heavy spare tyre around I have to agree there is some comfort in knowing there’s one 'in the back of the car'
I agree with you about the debris around factory roads, and I would add building sites/new housing, not sure if it’s since the invention of the nail gun but these places seem to have loads of nails laying around.
As for incorrect tyres pressures, an under inflated tyre will give you a bigger foot print therefore more tread area to pick up debris. Not only that I think you’ll agree the correct pressure keeps the air seal between the wheel and the tyre in place, if the tyre is under inflated the side walls will be soft and more liable to kerb/pot hole damage and deflation.
Incidentally I initially bought the compressor in 1998 when I used to do some serious 4x4 driving/off-roading where it was sometimes necessary to under inflate the tyre to improve grip and then use the compressor to re-inflate. I bought a cheap one as I expected it to get damaged, although (fortunately) it doesn't see as much use these days it still works fine and as I said earlier has save me (and a couple of friends) from having to change a wheel by a busy road side on several occasions.