How much is the minimal time for practicing Vipassana in daily life for achieving better mindfulness?

How much is the minimal time for practicing Vipassana in daily life for achieving better mindfulness? Is 30 minutes enough? I ask this question because I currently have some trouble being mindful, and (I think) it has become the source of many problems. If 30 minutes is not enough, perhaps you can give some suggestion based on your experience or the suttas.