Rosalie
A day from his last drink. It is not an exact science, mind. It would depend on his activity level for the time. With how he is going, it could be longer. And a caffeine crash is to be expected, but... at the most, he might sleep for a while, if you.. sleep. I know some of our kind do not.
At the risk of being a creepy old man, he is your husband. If it concerns you so, I'm certain you could... otherwise occupy him, burn off some energy.