It's funny how the greatest revelations come to us in thee strangest places. I'm having dinner in a shopping mall and all of a sudden, while thinking about why humans get bored, it strikes me that we are the ones who make everything boring. It's our brains, all the time!
Consider this: how many times have you closely looked at something as trivial as a chair? Look again at that same chair. And again, and again. How many screws does it have? How is the place where you sit your butt? Is it curvy, flat? What's the color off the chair? How much does out weigh?
Do you catch my point? You can walk the same path a thousand times and you will always, and I mean always, be able to see something new. The problem is that our brains trick us not to.
And this is probably valid for social relationships. There is always something new to talk about. You just need to train your brain to think outside the box :)