I have a different stance...
For me, I believe that communication, honesty/transparency is the

to having a successful relationship.
I stand on it!
I see no need to cheat. Just tell your significant other that you will seek affection/intimacy from someone else, if your significant other chooses not to be affectionate/intimate with you.
Intimacy isn't negotiable!
Life is too short to be playing games! If someone wanna do their own thing and not be honest with their intentions, then that is a cue for you to do your own thing and whatever happens will happen, feelings be damned!
How one starts a relationship should be the template of how things should go. People do change, evolve, etc. But, communication, honesty and integrity should always remain the same.
What is meant to be will be! It is what it is!