IDT I've been with anyone under 21 even in civvie life when I was a teenager. I was a late bloomer and didn't get laid until about age 21.
In the hobby, I've seen ages 20's, 30's, 40's and 50's. I have found the 30-50's age groups to be the best match, especially late 30's to late 40's. So, I would say I lean more towards the "mature" lady. At my age, there is more we can discuss, and I don't have to feel like I have to bang her incessantly to give her a good time. We have nice, relaxed sessions.