Without any personal experience to back it up, I'm reasonably confident in saying that the time frame varies for every family. Some couples can date for years and still never be ready to live together. With my husband and I, he came to hang out one night and basically never left. I was still living with my mom, and within 4 months we were moving into our own apartment. Things started great and have only gotten better.
So anyone who tries to tell you "that's too soon" is putting their own experiences into your life story, and there's no sense in that. If you all feel that you're ready then you're probably ready. From what I've seen, you all definitely have the compassion, communication, love and respect to work out whatever challenges arise. Beyond that it's basically logistics.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker