How many years we should put in studies after completing high school

I would say it is totally depends on the cource you join or the future plan that you have in your mind for yourself. I have spent 6 years after completing my high schools... I have done graduation and then post graduation which is also of 3 years of duration. So some people does engineering and get over with 4 years some take only vocational couse and comes out in 2 years and so on.. OS you decide that you want to do and do not count the years it(study) will benifit you in future... it will never be your hinderance in your way.