Heidi Winkel said:
...formal education alone has failed to prepare my generation with the skills, capabilities, and agility that we need to excel in the field
...it is a matter of identifying the program that will correctly align with the skills and weakness of the individual.
...What point in the career should one obtain a masters degree? I believe someone said five years. However, my concern is that there is a point that one can reach where learning formally how to do things would keep from hitting brick walls.
I may be in the minority, but I don't believe one should choose a master's program for the purpose of addressing weaknesses while glossing over existing skills. I believe that sort of specificity is best solved with specific courses, whether academic or commercial, such as for a particular software suite. In my master's program, wordily titled "Computer Education and Cognitive Systems," I was frequently dismayed and the class discussions were sometimes bogged down by K-12 teachers who were unholistically ticking off three graduate hours at a time, in return for small-scale pay bonuses; they seemed to think as small as that $50.00 bonus. Most of us were there for the scope+vision program as a whole. (Nothing against K-12 teachers, but too many in that program at that time were in the wrong place.) As an example, I firmly believe that rather than pursuing a full master's program to address a weakness in, say, storyboarding, an adult practitioner should first investigate the wealth of cheap-if-not-free courses available, and only then investigate the local community college, and only then invest ~$2,000 in a course from a commercial vendor.
Bear this in mind: "When I got my bachelor's degree, I thought I knew everything. When I got my master's degree, I realized I knew nothing. When I got my Ph.D., I realized it doesn't matter." Riffing on that, I had not fully understood before enrollment that my master's program actually offered several tracks, from AI to K-12 curriculum design to corporate instructional design to educational technologist, each with pros and cons. After the first six hours or so, and in consultation with the very good advisors, I chose to specialize in corporate instructional design. BTW, the K-12 emphasis was there as an inter-departmental political token to the College of Education, who lost several good professors to my relatively new program. The lesson here is to understand not only the options available, and actually evaluate those options and those professors, but understand also the programmatic emphasis of the university.
Regarding timing, five years is as good as any and better than most, I believe. As for me, I had two years in corporate skills training and two years in online training design and development. Fifteen years is probably too late. Speaking of senior professionals in the context of specific skills and topics: I've presented to many professional associations over the years (ASTD, STC, etc.), frequently with lifelong, mono-focus practitioners in the audiences - coaching only, sales training only, etc. These people are the neediest, because they've missed so much over the years while not educating themselves. For instance, in a 2011 preso to a local association about Articulate, I mentioned that Articulate Online is a cloud solution, but the cloud concept was completely alien to a few in the class.
And last, regarding the post-surname initials, I think it's posturingly silly to include "M.A." or "M.S." in routine signatures such as for emails. Ph.D., yes; formal listing on programs, yes; but otherwise, no. There are too many former "school marms" and their male equivalents who stretch into corporate training and post that Master's brag, which just makes it more ironic when they prove to have no experience in, say, project management or melding multiple software versions or ... Of course, I'm proud of my credentials (project in lieu of thesis, BTW), but I only display those initials on resumes and for presentations, to meet qualifications or establish credibility.
Your mileage will vary, of course.