I agree with you that all relationships are an investment and we all need to look at it that way. However it is an investment that is difficult to determine sometimes whether it will pay off or not. The key is as you say, to be honest with yourself about you and the person you are dating. This way you never really get surprised. Speaking as someone who has been in a ling term relationship and am exceptionally happy, I can say it all comes down to communication. We are very different in age, culture and many other things, but we have an agreement to talk about whatever is bothering us. It took some time to get this to really happen but now it works. Mostly because we both respect each other and want the relationship to be on solid ground. And also we are clear about what we each want and what the other wants. And finally, what the other wants we each want for that person. Not easy but the alternative which is getting ont he dating merry go round, is much more challenging in my humble opinion.