Fix a flat also has a shelf life. You can not just buy a can and expect it to work 1-2 years later. I learned this lesson personally the hard way. The goo solidifies in the can. Also on anything after 2007 has tpms (tire pressure monitoring system) here in the US. Fix a flat and slime will damage/kill the sensor (maybe not at that instant but it gums the sensor and plugs it) interesting side note, when you make it to the shop they can not let the car leave unless the system is functioning (once again weird laws apply) due to liability. sensors run from $30-$250 US.

the compressed air tanks are a viable option also, but they take up a lot of room and have a shelf life also. (they are like scuba tanks and can only be used for so long) personally i hate the things and they are a one time use until refilling, but it is a pretty robust system. Kinda hard for it to fail as long as you check it when you do your monthly tire pressure check.

I personally used a cheapo no name-brand one i inherited from my parents until my kids got a hold of it. As with everything else, they destroyed it. (purchased circa 1992...tod was 2016)

I am looking to replace mine so thank you for all the information.