Should I maintain my mindfulness 24 hours a day? I love mindfulness but when I sleep I loose all my mindfulness. I see dreams in which I am unaware of the Truth. 

Should I maintain my mindfulness 24 hours a day?
If yes , how can I maintain my mindfulness 24 hours a day so that mindfulness extends into my sleep?
Mindfulness will increase with correct, consistent practice. At some point, if continued practice occurs, the sleep cycle will be affected too, in the form of a lighter sleep with less dreaming and more awareness.

When balancing the Five Spiritual Faculties, Mindfulness is the only factor that is not balanced meaning one can cultivate as much mindfulness as possible without creating any imbalances in the mind. 

I would recommend watching the video "How Mindfulness Creates Understanding (The Buddhist TV)" by Ven. Yuttadhammo.