Uneven Relationships

Relationships where both partners give and receive and both get physically satisfied are great, but I'm interested in hearing about alternative "relationships" where one person gets more physical pleasure than their partner. I'm motivated by posts I've seen about gay guys willing to give blowjobs to other guys and they don't care if the favor is returned. Has anyone here ever been in a long relationship where one person gave more than the other and both people accepted it and were perfectly happy?

If you were on the giving end, what motivated you? If you were on the receiving end, did you ever feel guilty or did you just accept that you deserve the pleasure? Was it a "matter of fact" type of thing where one person just said, "I want to go down on you whenever you want it and I don't want anything in return."? Has anyone ever been in a heterosexual relationship like this?