How Much Mindfulness is Enough?

How much mindfulness is enough? Is moment-to-moment attention (the classical definition of secular mindfulness) just a suggestion for when we decide to give it a try? Or does it mean, moment-to-moment attention all day long? I'm not saying we can do it (or I can do it), but I think it might mean "all day long." It's a big aspiration. But then again, it's a feedback loop.