One of the problems with the old conventional green snot of death was the the heavy dose of silicate would drop out of suspension when stored for too long.
Descool doesn't have that problem and I know of no other reason to be concerned. If it were 10 years old, I might worry only because I don't have any idea if it has been validated for storage that long.
Not one dissenting opinion! Thanks. I will use the Dexcool in a 1997 GM diesel van. It came with Dexcool and we have had no cooling system issues. The van has 230k miles on it.