It is unfortunate that commitment is a dirty word in the modern day. I think BDSM relationships are simply mirroring the trends in society in general - where even 'til death do us part' is now a temporary thing.
In some ways this is a good thing - old fashioned ideas of marriage and committment can be stifling and sometimes dangerous, especially to women who feel trapped in a loveless marriage. The ability to have a divorce frees many women from domestic abuse and other problems. The same could be applied to a Dom/sub relationship. However, on the other side of the coin, there is the issue of the perception that these 'lifelong' committments are cheapened by the ease of seperation. There may be a compromise, however, the trick being to balance the ease of seperation with the committment behind the original agreement. Not an easy feat, however.
However, one thing I would say is that it should not matter to an individual what society or the lifestyle says about a relationship. What matters is what the people in that relationship say about it. If a collar to you is a wedding ring that must be earned, then make it so. What others choose to do with thier collars is their business and may well be thier loss. Eventually, however, even the most fickle serial monogamist (or even serial polygamist) may find themselves drawn to the need for stability in a relationship.