Hate to be a buzz kill, but I don't think vaping will improve the halflife of coffee.
I think the reason why cigarettes improve the halflife of coffee is because of the MAOI inhibiters in the cigarette, which are not present in e-cigs. Probably also the reason why people vape more nicotine with e-cigs than cigarettes, MAOI inhibitors that are lacking in e-cigs keep the body from breaking down alot of drugs.