Sexual expectations?

This guy and I really good friend turns out we have feelings for each other are hooking up but he is consistently worried about filling any sexual expectations I have (which are normal ones). He says I excite him so much he won’t be able to last long. I don’t mind that! I just want to have fun and enjoy. Is there anything I can do or say that can reassure him? I’m 24 he is 30. Age for reference.