I feel totally sympathy for those who find sex boring. It must be akin to losing one of the main senses, it is one of life's real joys, so if you've lost that, or (god forbid) never felt it, you have my total sympathy.
I love my running and am almost fanatical about my bike. but it can always wait for sex. I might add, that I've had my Bike a very long time, 27 years now, but thats not as long as I've had my one and only partner.