In my experience, a limited number of hours per day is much much harder than doing a limited number of days per week (or taking extended sabbaticals between projects). Both McKinsey and BCG are trying to make part-time programmes work, although they are still in their relative infancy and much more common for new parents than people who want to pursue other interests (though as far as I know that only happens to be the case and is not policy).One thing I would say about working part-time is that it tends to be less clean (due to client commitments, schedules etc) than it is meant to be. So for instance a person working 60% with two days off per week may actually end up doing nearer 70-80% and may have no pure and clean days off.If you want genuine limited hours per day and true flexibility, join a strategic policy unit in the civil service or something similar.