When does alimony end?

A California man must still pay alimony to his ex-wife, who is living with another woman in a registered domestic partnership, according to this article from WTOP news.  California is similar to Maryland law, alimony is terminated upon the death of either of the spouses, or if the spouse receiving alimony is remarried.   Some states, however, terminate alimony on co-habitation, it would be interesting to see in this law would also apply to a gay couple.  Alimony can also end when a specified amount of time is up (for example, payment may be ordered for three years), or it may be "indefinite."  Unless specifically agreed otherwise, alimony can be modified or terminated based on changes in circumstances.