Breechplug

I'll try and make this short. Since I now again will be using My Tennessee Mountain Rifle for some Hunting I'm looking to go back to GOEX FFFG as it shot this powder well with 90grs and a .490 Round Ball and .015 Patches. Well GOEX is hard to find and our local Bass Pro/Cabela's only carries Pyrodox and the other substitutes. I used to use Pyrodox RS in My Accura but I tried 2 50gr Pyrodox Pellets and it shot that so well I have since stayed with it. This past Season I bought some OLD Pyrodox Pellets and the second day of the season a beautiful 140-150 Class 8pt was following a Doe, I mouth bleated and stopped him broadside at 30yds, I shot and when I did all I heard was "PHHHHFFFFFFOOOOOFFF" I was like WTH was that, the Buck looked around, trotted back 30yds stopped looked around and than ran back after the Doe and down the ravine, I was Shocked and Depressed. I never had a problem with Pyrodox Pellets before. When I got home I noticed the back of the Pyrodox Pellets Box said 2017, and this was 2019. Old Pellets and probably not stored good caused me this Bad Day. I went and got a New box the next day from Cabela's and the rest of my season went well. I Vacuum Sealed the box and Primers twice for next season which I may or may not use but I want to be sure My New one's will work as I only use maybe 10 Pellets all season and the other 90 or so never get used, so if next year I buy a new box at least I'll have a good piece of mind and the extra $35 will be well worth it. Now to the GOEX FFFG vs Pyrodox RS Powders. If I buy a new bottle of the RS will it be any good next November or be junk like the old pellets I got this year? or should I wait and buy one then to sight in My Side Hammer as I really won't shoot it much as My Accura is my go to Muzzleloader. And what do all of you like better the Real Black Powder GOEX or the Pyrodox Substitutes? for Percussion Side Hammers? Will GOEX last longer than Pyrodox? I know I never had a problem with old GOEX but what is the shelf life for it when stored properly? As for the Pyrodox I'll never trust it again if it's not New. As for cleaning I don't see a difference between real BP and Pyrodox, When I used the GOEX FFFG out of my side hammer I had tight groups, how would the Pyrodox RS compare, has anyone had experience with the 2? Should I try and find some GOEX FFFG or try the Pyrodox RS? neither will be used up in a season as I'll only use the Side Hammer a few times in the season, so I'll try and store the rest, so should I go with GOEX for better storage or go with Pyro RS and just buy new each year? If you had a choice what would you use in your percussion side hammer? As I will use the regular Pyro Pellets in My Accura.