"Mature adults" is the key to the whole thing, I believe. My husband had been married at 23 (and divorced by 26). We met when we were 29, and married at 31.
I had not thought much about getting married at all; it wasn't a goal in itself, as it seems to be for some women (and for some guys). It didn't occur to me to marry, until I met someone I thought was worth it. :)
My husband and I were both over 30. I won't say which of us crossed that line first :~D
My ex and I were 38. My first, her third. I thought the warning bells were wedding bells.
*sigh* Live, and hopefully, learn.