I don't know if this is much help. My dh had similar problem too. He only lasted fewer than 10 thrust for years. But year after year, he got a little longer. Around 35 year old, I would say he was pretty adequate. But by then I lost all interest in sex, so I wanted him to finish quickly. Sometime I had to push him off and told him enough was enough! So they do get better when they get older if longer is better. I just hope you don't have to wait too long.
Another encouging thing I want to share was our sex life is good now. I actually can have orgasm since 2 years ago after being married for 18 years. I just wish we could have communicated and done something about it when we just got married. So many years wasted. Both of us were virgins and we have always been shy about sex, but it doesn't help our realtionship or our marriage. It all started to change when I told him I would work on being more involved when we have sex instead of pretending I was asleep. I worked up my courage to tell him what I wish him to do and he tried. It got better and better.
On the practical side, I have found reading a romance book or watching a romance movie before bed to get myself in the mood helps. Ask your dh to perform oral sex on you. When you are almost there, then let him penetrate. I would take over to continue to mastepate myself, and he would panetrate me and squeeze my nipples. I could come within a few thrusts so he doesn't need to last long. I have found I like slow, long thrust every 5-10 seconds apart. Anything more would make me lose the feel.
Once you are satisfied with the first time (several orgasms together), you may not need the second time.
Good luck!