It all comes down to your current position, your desired career path, and your means.
I list both my PE and my PMP on my company signatures, but that's because I am the technical project lead. The PE implies the degree, so no need to show the bachelors. Showing the Master's degree is only really needed on a resume when looking for a job, or working in the research fields. MBA's can be useful on a resume or company email signature, but IMO is like a PMP and job/project specific.
I am also a glutton for learning, but I do draw the line at practicality. I won't necessarily do a certification or a master's program unless I can see a genuine professional need for it. I've been debating getting a masters degree in Construction Management or a MBA, but it's been my experience that they never really make financial sense to do it unless you have the company footing the bill. And on top of that, a lot of Master's programs aren't worth the paper they're written on simply because most of the colleges that offer them are slightly better than printing presses to anyone willing to write them a check.