It's just an opinion. 20 hours (25% of the discretionary week, discretionary time is roughly 50% of 168 hours ~ 84 hours.) for me represents the maximum amount

It's just an opinion. 20 hours (25% of the discretionary week, discretionary time is roughly 50% of 168 hours ~ 84 hours.) for me represents the maximum amount of time that could be considered sufficiently diversified.