Caffeine levels in old coffee/tea

I have to wake up every work day at the ungodly cow-milking hour of 5:30 a.m. in order to be at work by 6:30. This involves a lot of yawning, and usually a caffeinated beverage of some kind.

This morning I was helping myself to some of yesterday’s iced tea from the fridge, and it occurred to me to wonder: do the caffeine levels in a cup of brewed coffee or tea drop over time? I know old coffee tastes a lot worse than fresh-brewed, but that doesn’t necessarily mean it’s less potent.

You guys are the smartest people I know, so I thought I’d ask you.

Come on – nobody? this is the Dope, man… you guys know everything!