Yes 20-30 years, yes right. Cool dry place in sealed ammo cans! Good job! also your right keep it with your guns and keep some cached where your going to travel with some more guns!
I got freinds that are wrong too, or tell me garbage like that cause they are jealous and/or not(truely or really or real) good freinds? While safety is important, what about opsec? Maybe he is not one to share that kind of info with. It is not dynomite and you don't have to worry about it that much. There is 100 year old ammo packed and stored well and it shoots great and people have zero trouble.