I had some gasoline stored for several years that I forgot about. When I opened it it was separated into water on the top and sludge on the bottom.
Using a fuel stabilizer, I think you can safely store it for about a year in good storage conditions. Without stabilizer it starts breaking down as soon as it’s stored & may bee good for several months.
I think propane can be stored almost indefinitely, but I’m not sure.
Liquid propane is stored in pressurized tanks and as you suspect is good as long as there are no leaks. If leaks should occur the gaseous propane is heavier than air and will collect in low places (basements??), creating an explosion/fire hazard. Therefore storage tanks should be outdoors and well ventilated.
Regards,
GtG