A lot of folks are asking us the question, and it is heartening so many already can picture us in a lifelong commitment. But we are happy as we are.
And maybe we are subconsciously trying to avoid a few difficult moments. My grandfather, for instance, is generally supportive, but may not wish to attend a religiously diverse (Calvinist and Jewish) same-sex marriage ceremony. He's in his late eighties; if we wait another few years he'll be dead and we will have avoided a painful refusal.
On my father's side of the family one aunt has come to see things from my father's perspective, the other sister is still holding out (their mother was blatantly homophobic). If we wait a few more years, maybe my father would have BOTH his sisters at the wedding, which would save him a lot of embarrassment.
On the side of my boyfriend, there are a few similar problems which might be solved with patience rather than haste. Discretion is the better part of valour.