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There is no particular resistance to gum formation compared to any other formulation of gasoline. It is true, the lead doesn't go away, so the octane is retained, but in other respects the fuel can certainly deteriorate. I was wrong in implying it is worse, but it is not any better than other fuels. The lighter components do evaporate in 100LL like other fuel, I just looked that up to verify it. Other than the octane preservation, I think the reputation for storability has more to do with sealed steel barrels than anything else. Apparently, barrels have been found at arctic outposts decades old and were still usable. Of course, Phoenix has a slightly different climate.

With Avgas you can’t legally add a stabilizer (unless one has been approved). So unless it is stored in the sealed steel barrels you will still have gum formation over time. Keep it totally out of sunlight at least. This is what I have found over decades to be the real killer. For example, you will see early gumming and black deposits in a clear fuel line or transparent fuel filter with any kind of gasoline.

Any fuel allowed to evaporate will have its formula altered. It's why you need tightly sealed, metal containers, or store it under very cool and dry conditions.

Gasoline evaporation builds pressure when temps climb and you need metal containers able to withstand the pressure to prevent venting.

Commonly available plastic containers aren't strong enough though I'm not too sure about commercial 55 gallon plastic drums. I have no experience with these but they do seem to be pretty well put together and the bungs seem to be pretty strong.

I highly recommend having at least empty containers on hand. Having been through at least a half dozen power out conditions from both hurricane and ice storms, I find fuel containers are some of the first items to disappear from shelves.

What I do, is I fill 'em at the first signs of trouble knowing I have an airplane with over 60 gallons of 100LL just a few miles away. :)

I lost power during hurricane Isaac a month ago, but only for three days. I only used my little Honda 2K generator which doesn't use much fuel and I still have 4 six gallon cans of gasoline that I need to use up.

Been using that in my motorcycle and ATV mostly. The motorcycle is a KLR that gets 65 mpg so it's taking awhile to use it up. Guess I need to fire up the Harley instead and do some cruzin'... ;)