lopram-
Whether or not having the CFI, II, MEI ratings will hurt you in the future remains to be seen (although I seriously doubt it.) It really depends on what is happening within the industry at the time. Obtaining these ratings however WILL benefit you several ways:
1. add ratings to your resume.
2. you will learn so much about yourself and flying when trying to teach others, which in turn makes you a better pilot.
3. gets you flying.
I wouldn't worry so much about not keeping your students if you are deployed. There will be other instructors for you to hand them off to.
Just like Rick said, your age is not of concern in the slightest. But... you don't have time to waste either.
My opinion is that obtaining your CFI is not a waste at all, given the reasons above. And lest we forget that even though you might be working on those ratings or instructing, what would stop you from applying with the airlines simultaneously? Fact is, it doesn't or wouldn't. That is still a ways off and who knows what the hiring market will look like then.
Press on... do what makes you grow and become a better pilot.
Lori