[NSFW] How do you tame a "death grip?"?

Prior to this summer my boyfriend and I dormed in the same building. We had sex almost everyday so there was no real need for masturbation. Now that summer has started both of us have had to take care of our needs by ourselves. However him masturbating about 3 times a day has caused him to have a hard time ejaculating during sex. We talked about it and he says he doesn’t want it to effect our sex lives like this so he’s going to cut down. I’m worried that it may not happen though. Have any of you gone through this? I know that masturbation can become an addiction and now I’m worried that he is addicted.