After years of marriage, some couples no longer engage with each other and merely coexist as roommates. Divorce incidence peaks at different times, says David Woodsfellow, a clinical psychologist and couples therapist and founder and director of the Woodsfellow Institute for Couples, in Atlanta. “The very top of the first wave is at about seven years,” he notes. “The very top of the second wave is 21 years. That second divorce is usually a growing-apart divorce. It’s about avoidance, not fighting.”