There's no need to take it on non-workout days. If your diet is in check and youre getting adequate amount of sleep, you're not losing out on much of anything by not taking it on non-workout days. Besides, people's body's get used to NO-Xplode because of that. Take it when you workout. You're saving yourself money anyways. I think that's a good enough reason to base your decision on lol.
and if someone feels they don't have to explain themselves to you then they don't have to