Burnout is a product of an imbalance of energy in and energy out. We all need a harmonious mix of what we have to do (energy-burning) and what we love to do (energy-generating). An energising leisure interest in today’s world is one that creatively expresses your natural talents for the sheer intrinsic enjoyment of the experience. Such an interest can generate sufficient energy to cope with long periods of stressful responsibilities (which is why I don’t use the word ‘balance’ that suggests equal time).
We talk about a fifth of the population having mental health issues. My focus is on keeping the other four-fifths mentally fit - the sort of mental fitness that sustains strong personal growth and positive behaviour. People who say they love their job so much that they don’t need leisure interests need to have a good look at the literature on the effects of workaholism. Work contains an energy-burning stress factor that needs to be regularly countered by a mentally-energizing complementary leisure interest.
A harmonious mix of energy-in and energy-out interests is the way to go. It's not how long a vacation should be but what it does for sustaining your mental fitness.