Stop in for a cup of coffee

So question. How long can a carb sit new, in a sealed air tight box with Oxy absorbers and still be ready to use right out of the box?

I’m gonna rebuild both these carbs, just cause. But the intent is to have them identically set up so that if one fails on me during power tour or HRDW, I can just bolt the other on and go.
I have carried an extra ceramic resistor thing-a-ma-bob in the glove box but never needed a spare carb.