My wife had a b/f for about ten years, a very close friend before I met her, but not then a sex partner. When we ventured into the lifestyle, she called him and she saw him off and on for ten years. This was prior to HIV. He was our first venture into the lifestyle, she went to him, and she spent hours with him and came home to me. We were both very excited and we were undressing her as she recounted the evening and at one point, she started pushing me down, and down. When it dawned on me what she wanted.... duh.... it drove me nuts, the idea of eating her and the fact that she wanted it. I'd never see her that excited in all the time we'd been married.
And, of course, in other ventures she always preferred our guest go first. Who was I to argue? She just loved the idea of someone else's cum being there before me.