To state that you no one will spend BTC because it will go up in value long-term is a logical fallacy. By the same logic, since USD is easily convertible into BTC, one could argue that it's wiser to buy BTC with your USD instead of buying groceries.

That being said, you should do both. Have a stash in cold storage that you hold long term, and when you want to spend either instant buy and spend right away, or spend and immediately replenish.