About two years ago I lost patience with fixing flats during my training rides. I had at least one flat on every ride out, and some times much more. On a single four hour training session I once managed to use a full pack of patches and a spare tube, and I still ended up having to carry my bike to the metro to get home. This was too much - when I get a chance to ride, I want to spend my time riding.
The first solution to this problem that I tried, was adding a sealant. The first product I tried was the Schwalbe "Doc Blue" sealant. The idea is that you pour some of this liquid into your tubes and then ride as usual. When a thorn or nail or other object punctures your tire and inner tube, the sealant will seal the puncture and you will ideally never even notice that you had a flat. The sealant will work almost instantaneously, so the drop in tire pressure due to lost air will be insignificant.
This did not work well for me though. It "almost" worked - but it seemed that the object that punctured the tube would stay in the tire and continue working on the punctured tube so that the sealant would never effectively seal the puncture. During this process, the sealant would leak out of the inner tube and into space between the tyre and the tube. So, when I eventually ran out of air and had to fix the flat with a patch anyway, the tube would be soaked in sealant on the outside, and wiping the tube down to make the patch stick would just add to the inconvenience of having to fix the flat in the first place.
Using sealant seemed promising at this point, but clearly it did not work for me to just add it to the tube. I also did have a few "snakebite" punctures - due to running the rear tyre with low pressure and being careless when jumping obstacles. Of course the sealant could not fix those (typically these are 1cm long cuts in the tube). The solution to snakebites is to lose the tube - to run tubeless. Since it also seemed that the tube/tyre combination was what caused the sealant to be ineffective, I decided to give this a try. Since I am on a budget, I went for the cheap option; the first setup simply used regular non-UST tyres, Joe's no-flats rim strips inside my usual Mavic Cross Ride (non-UST) wheelset and the Joe's no-flats sealant.
This turned out to do the trick! Early on with this setup I experienced a puncture during a race; I noticed the "pfffft" sound of a flat on my front tyre and after two revolutions the sound was gone, the puncture sealed and I did not have to stop to inspect the tyre for thorns. There was one problem with this setup though; regular tyres are not meant for tubeless application so they generally have thin sidewalls that are not air tight. The sealant will solve this problem to some extent, but not completely. All in all, I never managed to get my set of Continental 2.2 Mountain King tyres to hold air between rides. They would hold the air fine during a ride (because the sealant would constantly be swirled around the inside of the tyre sealing any microscopic holes), but the next day they would be flat.
The solution to this problem was to simply buy real UST tyres. Tyres meant to be run without a tube. These generally hold their air - well, I have three tyres mounted on rims and two out of three hold their air. That last one loses air over a week or so. To me, this is perfectly acceptable. I have not had a single flat for two years on my mountain bike. This is absolutely fantastic - it means that when I get out to ride, I actually get to spend my time riding.
The major downside to running "flatless" (tubeless with sealant), that I have noticed, is: Limited availability of tyres - there are only very few models available in UST variants. If you are very picky about tyre choice, this may not be acceptable to you. Personally, I am perfectly happy running with a 2.2 UST Mountain King on the front, and having the choice between either a 2.2 UST Race King (for dry days) or a 2.4 UST Mountain King (for muddy days) on the rear.
Another downside would be that it is a lot more complicated to change a tyre. You do not want to change tyres on your rims just because the weather changed - you only want to change tyres when they are worn out. You need to dispose of old sealant, dismount the tyre from the rim strip (which will often be sealed tight) without damaging the rim strip, get the new tyre to mount cleanly to the rim strip, inflate the new tyre so that it seals against the rim and of course add new sealant. My solution to this mess is to simply have two rear wheels mounted with each their tyre, complete with brake disc, bike computer magnet and casette. So, when the weather changes, I change the complete rear wheel - this is slightly more expensive than having just one rear wheel, but it is very convenient and completely solves the problem with tyre changes.