...ALL relationships are temporary: in marriage it is either by death or divorce. People change, people move. To say that we shouldn't engage in relationships because they might end is foolish.
I didn't say one shouldn't engage in relationships. I said someone shouldn't date another if it isn't going anywhere. If it's purely for entertainment and emotional pandering, it's milking an emotional cow. It's not right to invest or to let people invest themselves into something they will inevitably develop a feeling of ownership or entitlement from and feel betrayed by when it's revealed that they're going to start pouring themselves into someone else instead later. Whether you admit it or not, there's a feeling of betrayal by the person who didn't decide to leave when they were ready. It's just a bad idea, in my opinion.