Naso, at your age, 15 years is a HUGE difference. The woman is old enough to be your mother! I don't think it is healthy...and probably not good for your self-esteme or reputation.
Let's be honest - it probably means that woman was desperate and had a low self-esteme to begin with. Healthy relationships involve people who have good self-esteme.
Hey, it was probably great sex. And he has a point. Older women are less into themselves and texting for the hell of it. Women his age are generally great to look at, horrendous to talk to. Too old could be a problem with biological clocks and stuff. As long as it's purely physical and he doesn't get roped into marriage, it's fine.