That is why I carry the C02 inflator with extra cartridges.
Before I started carrying it I was on a group poker run and got a nail. Another rider puller over and offered his plug kit. It was easy to find the nail, pull it out and plug it up. Then we both sat there staring at a tire with the hole all fixed but still no air in it.
I think there are lots of people out there carrying plug kits and no way to fill the tire.
Don't be one of them!!!
As for the compounds you put in your tire to "prevent flats", I have personally never been a real big fan of them. Even though they save they don't throw off the tire balance, I can't see how just riding and depending on centrifugal force to randomly spread the compound to the walls can ensure it spreads evenly.
Besides I would rather KNOW when I have a flat. Even if it takes me a few minutes on the road-side to repair it, at least I know my tire is compromised and I need to get it changed. With the compounds, you get a puncture and the goop immediately seals the leak. We know that is not a permanent fix, and now you are riding on a compromised tire and don't even know it???? But I guess on the flip side if your tire doesn't go down from the puncture you do not have the safety concern of going flat at highway speed. So you need to weigh the options and decide which is more comforting to you.
Run with Ride-on tire sealant in rear tire for a year without any problem after a puncture. Was able to remove all wheel weight because the Ride-on did a good job of balancing the tire. While using tire sealant, you should check tire often. Good stuff.