Let me differ from others.
Well other professional Paper certificates(based on technologies) expires, and even masters degree certificate would expire . too.The difference is, one you can be pretty sure that it would expire within a short time the other one has a slim chance.
But all in all when it comes to knowledge both can behave the same or you might need to unlearn a lot of junks before you can be useful with your masters.
Masters brings confidence,pride and other kind of things to boost one`s ego.Sometimes masters reminds you of what you didn't study seriously in your bachelor Degree,because you thought were inapplicable in real life.
You can make few choices before you decide why you need a masters Degree, what do you want o achieve after .many people go for something different (to compliment)after realizing that they need to move where money and pride reside .E.g from computer Science to MBA, or to Security etc.
Remember you will always need to practice or go for refresher causes regularly.