Measuring life balance through discrepancy theories and subjective well-being

The concept of life balance implies that there is some optimal time allocation between the various forms o(human activity we engage in each day. So life balance can be measured by the size of the discrepancy between how we should and how we do allocate our time.
If someone chooses to spend all of their discretionary time writing poetry, is this a balanced life? Many people would say no. They would judge such a life to be imbalanced because life is full of competing demands, and writing poetry all day means that other aspects of life are neglected.
But is this just an imposed value judgment, or does the concept of a balanced life have deeper meaning? The answer must lie with whatever we use to measure the outcome. Any conclusion that balance is better than imbalance must be based on empirical evidence. So, what should be measured?