Labial size has nothing to do with sexual activity. Every woman's private parts look different, just like looking at their noses or eyes. There really is no standard. Some people naturally have bigger labial lips, some smaller. Some have a rather exposed clit, some are completely covered by the hood. You can swell after sexual rigorous activity, but that always goes away in a short time. Usually, by the time you are in your teens, what you have is what you're going to get - like with your breasts. They both start and stop developing around the same time (except if a woman gains weight, her breasts will continue to grow - not so with your labia). You can have sex 100 times a day or die a virgin nun, and everything will still be the same size on the outside. The inside of your vagina will change over the years depending on the number of children you have and whatnot, but the outside parts you can see stay the same.
I can't really comment on men's testicles since I don't have those body parts, but I have seen a few in my day. I think when they get older, the sacks tend to elongate a little which make the balls extend down some. Of course, when they are cold, they shrivel up close to the body. That is a natural response to keep the sperm at an even temperature. When I guy gets hot, they extend away from the body. That's because if sperm gets too hot or cold, it will die.
Mens Testicles Are The Same Way. Just Like How Some Men Have A Larger Pennis And Some Have A Small One. Some Have Large Testicles And Some Have Small Ones. What You Get Is What You Get. I Have Herd Of Surgeys You Can Get To Change How You Look Down There But I Don't Know. Hope This Helps A Little.