Coffee isn't milk, fortunately. It certainly is not a health issue.
There is a lot of slack in the expiration dates. There are 6 and 9 month expiration dates on k-cups that I am aware of. There is no rhyme or reason to it - so if you see a 6 month k-cup, you're probably good for another 3 months minimum.
Over a long time, the oils in the coffee may turn rancid. That will make it taste more like commerical grade coffee. Some people actually like that, because the coffee tastes stronger. Not better, just stronger, and some people don't know the difference.
Try it, let your taste buds decide. let us know what you find out.