I'm curious to know the answer to this as well. I could understand that with a BDSM relationship it requires more. At least in my opinion. For instance, effort, trust, communication... These are all things that will increase in a D/s relationship. I feel though that my year of devotion to my Master is still a year. In all honesty, I have zero desire to serve another... Ever. I've thought about the possibility of being able to, but it always comes back to the same thought. I don't think I could.
Also a comment was made about worth. I feel its a great point. Even though jealousy surfaces on occasion with new "threats", my Master saying things such as: I'm so proud of you -and- you are My one and only -and- you are the only cherry on ky cherry tree ... Well, it's the reassurance that I need to make all jealousy subside. If you have an honest relationship, comments of reassurance must be taken at face value and should in turn be comforting.