It's all very well to sit somewhere with M.D. after your name, thinking that years upon years in University won't do you any harm - it won't because it can't if you HAVE to do those years before you qualify in ANYTHING.
A Master's is quite another matter: consider your peers that do not go for the Master's, because by the time you qualify with it, they could well be your Boss even although you are supposedly better qualified. No matter what qualification you leave higher education with, it only stands as proof that you can memorise something and then regurgitate it when required. The workplace is an entirely different environment, requiring you to exercise and employ a completely new skillset to what you have learned up to that point.
No matter what your qualifications you will start as a junior until you can be assessed. Then there will be criteria you must adhere to, deadlines to be coped with, interaction with colleagues (some of whom you may even dislike), interpersonal working relationships to be forged and above all you will have to justify what you are being paid for your contribution to the Company.
While you are achieving your Master's, your peers from a year ago will be climbing the corporate ladder, then you will arrive a year later - at the same place down the ladder that they were at last year.
I qualified after 3 years, then did my Post Graduate year after 20 years. First class education doesn't have to come as a package deal. But life does.
Your choice.