Even though monogamy had never really made a lot of sense to me, I'd allowed myself to be assumed* into a series of monogamous relationships from my mid-teens to my mid 30s. Finally I'd had enough and had managed to scrape together the intestinal fortitude to tell my now-BF that I wasn't looking for a happily-ever-after one true love deal when he asked on our 2nd or 3rd date where I saw the relationship going. He said "Oh, ok. You're Poly?"
*Exclusivity tends to be assumed over here from the first date on. I gather it's different elsewhere, particularly in the US.