Post Graduate Degrees in the 21st Century

A lot of of my colleagues and high school friends are enrolled in different grad schools. This begs me to ask the question if grad school is needed to succeed especially in a corporate setting. Coming from a second tier college in my country, I have deduced that I do need this in advancing my career and to help me better prepare for a life in business once I decide to leave the corporate rat race. But do I REALLY need this? Am I just wasting my time and money reviewing what I have already learned in college and in my 5 years working? I do home I reap the rewards once I finish this in 2 years.