There is a possibility that they would be happy in their middle adulthood and most probably their marriage will flourish. In many cases, a happy marriage is equal to age, maturity and career orientation. If Carl and Jenny were married in their late 20s most probably both have stable jobs and are happy with it. They will be able to learn to compromise. If they were dating for a longer period of time, most probably, they know each other well enough to accept their strengths and flaws. Marriage is also base on respect and communication. If they have these, plus a good career, then they will be happy and will stay married til one of them dies.