Store up
Definition 1 of 3
Pro Tip 1/3Emergency Preparedness
Relates to keeping essentials for unexpected situations and self-sufficiency. 
Families in hurricane-prone areas often store up bottled water and canned goods.
Pro Tip 2/3Not Just Physical
Applies to abstract concepts, like money or digital data, not just physical items. 
I've been storing up frequent flyer miles for a trip around the world.
Pro Tip 3/3Long-term Process
Implies a gradual accumulation over time, not an immediate action. 
We store up supplies all year to donate to the food bank during the holidays.