Thanks for the info, Don Nom!
Having said that, I'm personally of the opinion that tequila is fine for a decent amount of time until there's less than ~1/4 bottle remaining. At that point, it's far more satisfying to invite a couple good friends over and finish it off in one sitting. No need to get too attached or sentimental.
- SeattleJuan, jdjohn84 and Don Nom like this