Does he seem like he's only trying to get off to pleasure himself?
For me (male,31), I do like to get off for myself but really enjoy making my girlfriend feel good; where it includes manual stimulation or whatever.
When your boyfriend is done, couldn't he stimulate you another way?
Or maybe even bring toys into the relationship; if he's open to that...
I've heard that masturbation before sex can also extend the time to reach and orgasm...