Continuation, yes again:

Let move into the area of "relationships" for a second, how far does "physical attraction " really pull the relationship or propel even. To what extent does the relationship start to demand substance from both participants, at this point does the relationship fall apart or both individuals realise they were never a good fit.

This reminds me of something i heard a while ago "we spend too little time deciding something that will determine the course of our life" , for instance the environment you live, your spouse. Your school. All these decisions have an immeasurable impact on quality of life in the long run and we spend an comparably small amount of time thinking about them or even considering the pros and cons.

Say you spend a second to think whether or not to interact with someone you think you see yourself with, how long do you project the relationship will last.

While i am definitely not an authority on this, i can simulate the effects to a large degree i think. This brings me to the point of this, "common interests ", many individuals have varying interests, let's consider for a second that there is a perfect match for everyone, someone that matches your interests one to one. The odds of that are ridiculously small when you consider how out of pocket some of your interests might be.

And if, there are no intersection of common interests, does the relationship not disintegrate into a blob of monotony and mediocrity?

If it doesn't, how do you keep it alive to any degree?