I don't view it as a 'lifestyle' because that feels like its a fashion accessory.
But BDSM isn't roleplay for me, it doesn't just define me or my relationship, but it is part of who I am. Role play signifies something that isn't real or truthful but pretend, and although role play can exist within it (ie - medicalplay in a sense can be a roleplay if someone is a doctor and patient - or rape play - which can be taking on defining roles) BDSM is not about roles persay.
*edit to add that BDSM isn't just about being serious, it is about having fun and a laugh too. It's just about living.
Peace and Rapture