For me the concept of a dead end relationship is one where there isn't any signal that goals are being met. For instance an eternal engagement. Or no attempt to pool resources and make a go at it. It's a relationship that is stuck in neutral. It's one that's without progess. It's one where the actions don't match the words. It's one where one side senses this overwhelming sense of frustration because needs are not being met and the future of meeting those needs is rather bleak. One wakes up years later, typically, to realize things aren't getting any better while typically they feel even worse.