My boyfriend is mono and things have gone well.
But then again our lives are compatible. I split my time equally between my husband and my boyfriend. Near one is higher than the other in importance to me.
So it can work just fine.
40 yo straight female
Married in the eyes of the government to Butch since 2001...
Murf my monogamous second husband has been with me since May of 2012.
In a V relationship with an average 60/40 split of time. Only due to Murf's and Butch's crappy work schedules.