I have to second the rock analogy. My husband is my other half, my shelter from the storm, the one I can count on no matter what, who will ALWAYS be there. No matter how crazy and chaotic life gets, I can count on him to hold me and make me feel like it will all be alright. He would be this if we only had sex with each other, if we had weekly orgies, or if we never had sex at all. None of that affects the emotional support he offers.
My boyfriend is ALSO the love of my life. I also intend to spend the rest of my life with him. But, even though our love and commitment is just as strong, it IS a tiered system. Should there ever be a situation where supporting or helping his wife meant leaving me, then that would be the choice he had to make. I can only imagine this coming up in some crazy far fetched scenario (like going into witness protection or something), but we still know that in that crazy, hypothetical situation, his marriage comes first.