Do you miss being with other women in a long term relationship?

This is more of a curiosity of mine as i’ve been in one long term relationship (3 years has been the longest). Near the end of the relationship I brought up how it made me feel insecure and uncomfortable how I’d see on her phone that she would save posts of women she found attractive or would watch porn. She however expressed that it was nothing serious and just part of human sexuality. She expressed how she might feel attraction to other girls but that she would never act on it and that it doesn’t diminish her attraction or love for me but was simply fantasy. I however don’t think I experience this. I might notice an attractive woman but it lasts nothing more than the second I see her. I’m not big on porn but I might indulge in some reading. I however get off pretending that it’s my gf and use my imagination that way. I know people are different so I guess I just want to see different perspectives on this!