I am in an sl relationship with a girl and we keep it in SL. My gf and I are exclusive to one another so we spend our time together but when either of us is not logged in we are able to have playmates or friends with benefits. It works for us because we know what to expect and we talked about how the relationship was going to work. Communication is key to any relationship in SL. Also we both make each other a priority in SL. I noticed some are not willing to put their partner’s need/wants in front of their own.