Different sexual tastes

My partner and I have been together 7 years and lately our sex life has fizzled out. Im deffinately the kinky one he isnt into some of the things i am but im okay with that as hes usually so attentive in bed that we still have excellent sex. But lately hes not been that into it. Our sessions used to last at least 30 minutes but now im lucky if it lasts 15 mins. Im not sure what to do. I love him but I dont know what to do ive tried speaking to him but he just said hes been tired lately. Any one got any advice ?