I've been in a serious, intense BDSM relationship. It lasted just under a year.
It doesn't really answer your original question, since we found each other through the scene (long story), rather than introduced it later, but for the latter question...
The only concern is that brighter candles burn faster. Because the power exchange, at an emotional level, was so intense we kind of burnt through the various quirks in our personalities very quickly. Arguments became more intense, both because of how... deep, for want of a better word... the relationship was, and also because, as the submissive side, I couldn't raise issues when I needed to, so they... festered, I guess.

Perhaps now, with hindsight, we'd deal with the issues better and understand how to work around them, but then they became impassable obstacles.

Anyway, for what it's worth, physically it was awesome