Well... I think it's ok for me to comment, yes?
Right up front, I'm in the boat with Helly. No infidelity allowed. It's just not an aspect of our relationship. I know that's ok with some folks, and that's totally fine, but we're dedicated to each other and there is no room for anyone else in our relationship.
As for the other, the looking and the physiological and emotional response to the looking... Looking is as normal as breathing air, eh? We look at folks and we recognize that they do or do not appeal to our sense of personal "taste" in terms of attractiveness. It gets murky for me if the response to the looking moves beyond a fairly dispassionate, "Oh my!" What is missing in the relationship that the looking has moved beyond the "gazing at art" type of thing?
I can honestly say that whomever I consider attractive does register on my conscious, of course! But, it's more of a disinterested sort of "Oh my!" than it is a "whooohoooo baby bring it over here" sort of thing.
Does that make a bit of sense?
I guess, for me looking is totally normal. The response to the looking is the definitive thing.
I think for those couples who have problems with even the looking, "What are you doing looking at her/him!?" that is an indication of something more deeply wrong in the relationship.
Now, having said all that I will totally admit to being hopelessly old-fashioned in my thoughts on this sort of thing. :spring: