Our vet told us to feed canned pumpkin to our long haired cats as it would help 'bind' the fur from grooming themselves and take it out the 'correct' end instead of having hairballs on the carpet! It worked.
Years later, with a new kitty who didn't adjust well to her first home, another vet told us to use canned pumpkin with any changes in wet food. Worked.
As to stocking up, we don't use it all that often. There are a lot of 'alarmists' out there these days.