I'm no #polyamory expert but ... "we fuck other people to keep each other on our toes" doesn't seem like the healthiest way to conduct a relationship.
Bonus eyeroll points for including this bullshit: "I think it’s a little selfish to expect one person to fulfil all your needs, until one or other of you dies."
(Monogamy doesn't expect that either - it's why we have *friends*! https://www.girlonthenet.com/blog/argument-for-nonmonogamy/)