Finally, in TSS, we get to find out the age of Our Fave Ferret: it's around forty-two! We know this because Kapista Kirov's papers (which match Q's physical characteristics precisely) list his birthday as October 29, 1937, and his age as forty-two. That might be a couple of years off the real age one way or the other, but Credentials wouldn't have made it too far off, lest it raise questions in the mind of a suspicious official.
Now, this information is certain to rekindle an old debate in the Q-mmunity. Say in TSS that Q's in his early forties (and this means Shadow Exec's recent "ball park" guess was probably not too far off); that means his first Q-orpus mission (TB/QM, 1965) must have occurred about fifteen years previous, when Q was around 27 years of age. That works for me; it would've given Q time to have served in the military (though certainly *not* in the "Churchill War," as Oktober accuses him of). On the other end of the aging process, being forty or thereabouts in TSS would've meant Q would be about fifty-six years of age by the time of his final Q-orpus mission (QBal, 1996). That also works perfectly well for me; though fifty-six would be past formal retirement age for many professions (and retirement ages are definitely trending upward), one has to take into account that Q's creator, Elleston Trevor, took up study of karate late in life, achieving high proficiency in the sport nearly at the age of sixty years. Thus, fifty-six wouldn't have been all that old for either Quiller or his creator.