I'm 51, and my instructor is probably in his mid-20s, which is fine by me.
In fact (and I know this is a bit of a religious argument when it comes to training, regarding mix of basic piloting skills, technology in the cockpit, etc), although I wouldn't have refused an older instructor, my preference was somebody younger who had "grown up" so to speak with all the modern technology in the cockpick, and was prepared to teach that along with the basics.
So far, I'm very happy with my instructor and feel it's a good fit. I feel I'm learning what I need to learn, at a pace that's good for me, and I don't feel like anything is being left out. I'm getting exposure to a little of everything, while still focusing on the basics.