Nope, not too old to enlist and still be a 34 year old E-4/SPC 4 (Old army designation)
The maximum age of non-prior service enlistment, under federal law used to be age 35.
http://usmilitary.about.com/od/joiningthemilitary/f/faqenlage.htm
USAF was before your 28th birthday.
Yes, of course, but how many actual 34 year old spcs. are there? Damn few I would wager.