I believe it is always a bad idea to go don't ask don't tell. How could that work if you are open in communication. Communication is super key. You can actually learn some new things by talking about your experiences.
Maybe you thought you knew your SO but then learned that someone else did something and they liked it. Now you have just added more to your primary relationship then you had before. It also opens the door to being more compassionate and really opens the door to learning more about yourself and your SO.
More people actually could fall under poly then they think. Ploy isn't about just having sex, it's about relationships. Think about when you have had a friend in your life where whenever they needed something you helped them. Could that have turned into something more if you would have allowed yourself to share those feelings? But maybe you didn't because you were with someone else and so you kept doing things to be near them.
I am not saying you are having relationships with everyone who is your friend. However, some friends share different parts of your life then others. If you can juggle many friends, maybe you can have multiple lovers.![]()