There are two variables
- The degree to which you can have a conversation with the person.
- The degree to which you wish to fuck the person.
And three types of relationships:
- You talk to the person only in order to fuck them or to maintain a relationship that involves sex.
- Sex is a spinoff and/or expected consequence of a really good conversation.
- Both sex and conversation are great.
If you are in the first type of relationship, it won't last.
If you are in the second type of relationship, you'll either end up friends, or part ways.
If you are in the third type of relationship, this is a person to marry.