I think 80 is a better level. People living in Spain and similar regions, who work outside most of the year, have levels up to 220 and they have no problems with it. You should not pursue that value via supplements. Taking 2000IU or 4000IU daily is healthy, but go much higher for longer periods and you end up with calcification of your bones. That's not reversible, and it might kill you in the end.