Hi there Ryan!
If you kept the powder sealed in its original container, in the dark and somewhere dry as well as cool the shelf-life would probably be measurable in years not weeks. No joke!
If you kept it sealed in a commercial freezer (minus 30 C say) its shelf life would be virtually indefinite.
The main thing is to keep the stuff dry. Bacteria cannot degrade the material without sufficient water. Likewise temperature, every 10 degree drop in temperature halves a rection rate. Once the temp drops to about 3 degrees centigrade bacterial growth pretty well stops.
Keeping the stuff sealed means that oxidation is pretty well minimal too.
I've used amino acids, whey and egg white powder three years out of date just by watching the storage conditions. They were fine when I finally opened the tubs!!
Obviously you will be opening the tub every day, so why not order a spare (smaller) one and decant half the material into it and put it in the fridge/garage/hallway/garden shed etc? That way each tub will only be exposed to oxygen, moisture, heat, light etc 41 and a half days!!
Hope this proves helpful!!