Of course, this change would come with a whole host of health benefits - which, naturally, translate to financial benefits for the boss. Workers will probably find they need to take fewer sick days or personal days away from work, avoiding conditions from depression and anxiety, to cardiovascular diseases stemming from sitting all day, weight gain, and productivity-denting fatigue, with a huge array of afflictions and troubles in between. In addition, employees would be happier, having had more time to spend doing activities they truly enjoy and find fulfilling, and have a much more positive relationship with the business. Undoubtedly, this would translate to much better work being produced - particularly as it is far easier to concentrate for 6 hours than for 8.
The consequent division from personal time and professional time would surely be a relief for most people, with an implicit agreement being forged within these 6-hour day businesses and their customers not to contact each other for business-related matters out of hours. This means that even if you choose to allocate yourself another couple of hours of work per day, even on your own time, you can count on having the evening and weekend to unwind, without being interrupted by work calls or emails. This break is absolutely crucial for psychological well-being, and to give you the opportunity to focus on other important areas of your life.