That idea is that the longer one is married, the longer a person will come to depend on a spouse and get used to the lifestyle of the marriage. The main reason for permanent, periodic alimony is that, after a certain amount of time, a person gets used to a certain style of living and should be able to continue to live in that lifestyle. How used to a lifestyle can a person get in only six months? Therefore, permanent periodic alimony isn't generally awarded unless the marriage has been a long-term marriage.
