I mean, that’s cool, but you haven’t actually adressed the problem, which is that I’ll spend 3 months training you, only to have you quit after 9 more. That’s not really a good investment
His point is that it will only take a month to get him up to speed, not 3.
But I agree that a better answer would probably be something along the lines of "I have so much experience that I deliver in a year what the average guy would give you in 5; and if you're good to me, I might well stick around as much as I did at X", or something along those lines.
