I haven't played casually either, so as the others I can't comment on that. I know, however, that in the past the BDSM aspect really was a strong glue for the relationship I had at that time. In a way BDSM is a big common interest, don't you think? Additionally, it comes in the package with trust and respect and tends to eliminate the power struggles that are common in vanilla relationships (at least that's true for me). I don't think, though, that it's a glue strong enough to hold a relationship together. There needs to be some other things to hold on to...some things you have in common, some things you can explore when reality kicks in and neither is in the mood for kink. Just my two cents