Re: Retumbo shelf life
I bought a 200 pound container of WC852 powder in the early 90s. It was made in 1972 and stored in a copper lined keg. It has a rubber seal and I'm still using out of that powder to this day. I use it for my practice ammo because it was so cheap at the time.
BTW the only thing I've seen deteriorate in less than 5 years is a recent batch of primers. They still go bang fine but the accuracy went from great to sucks pretty quick.
Get as close as you can, but utilize your skills as needed.