Wow, you're really being pushed into the Nichomachaean Ethics, aren't you?
So, Aristotle argues in the aforementioned text that virtue is a state of being. It is a posture you must accustom yourself to holding, a reaction/manner/metaphorical muscle memory that requires flexing in order to maintain it. That is to say, virtue is not something you just learn and then never use.
In the context of exercise, Aristotle's concept of a virtue would be (this is a painful metaphor to make) like a pushup. Just because you once learned how to do a pushup does not mean you are permanently "fit". You have to actually exercise that pushup to build the muscles, and then you must maintain those muscles.
In this context, a virtuous life is the muscle memory acquired by practicing the virtue you learned.
What, according to Mill, is greatest happiness principle? Exactly how does he think that principle can be used to determine whether a proposed course of action would be the right or the wrong thing to do?
How easy or hard is to to apply the utilitarian "hedonistic calculus"? Does performing these calculations require us to know exactly what will happen in the future? If not, how can we be confident that we understand what the consequences of a proposed action will be?