The biggest age difference for me was approx. 29 years. I was 19 years old delivering pizzas on the weekends in college and had a regular customer who was a pretty divorcee about 48 years old. She eventually invited me in, changed into a nighty and plied me with wine, lol. It became a regular thing that I would take a few extra minutes for delivery or would just end up there as my last and spend the night. She was slim and petite and did not look her age and was very patient but very voracious. She definitely contributed to vastly improving my stamina.
Recently I developed a fling with a much younger girl - I am 47 and she is 25. We had been friends for a couple of years when she broke up with her long time steady. We ran into each other randomly in a local bar after we had each had already had a few. She poured her heart out and was upset that she couldn't find a decent steady guy, then asked if I would "do her a favor." When I said, "Of course, I'll do anything for you" she got up and whispered in my ear "I really want you to f me." And so it began. She has since gotten back with the guy but says she won't give up the best sex she ever had so we have kept it up. A little bit of guilt there as I am friends with her guy, but I can't break it off without hurting her and she is really hot and is almost always available.
The biggest Iguess "maturity" difference was when I was 17 and a 13 year old sister of a girl I was seeing hit on me in the sister's bedroom. I was already all riled up after making out with her sister when her sister left the room to go deal with younger siblings. She told me she "really wanted to do it too" and started kissing me and pushed my hand up her shirt and next thing I knew she was naked. I couldn't say no. It was amazing. She begged me not to tell her sister and I never would but i was afraid her sister would find out anyway. I eventually convinced her to let me tell her sister that she was curious about seeing a guy with a hard on and brought her in the room while making out with the sister. We ended up doing some back and forth playing and her sister ended up being cool with sharing. Definitely weird being with two sisters, especially since their much older brother would sometimes give me a ride home afterwards. He knew what was going on with the older sister and said as long as that's what she wants it's cool, but I was scared to death he would find out about the younger one.