I guess it's probably different if you get into a relationship while still in high school or an established adult with your own place to live, but my partner and I were pretty much living together within a month. We're both in college and I basically moved into his dorm room. My (university assigned) roommate was a mess and I was tired of dealing with her coming in at 3 AM high out of her mind and deciding to bake cookies and his roommate was his sister, who spent 98.5% of nights at her boyfriend's apartment. Since he had the space and I wasn't getting enough sleep in my assigned room, the simplest solution was for me to start staying there. My assigned room became more of a place to store my things and I generally only went back to get clean clothes every few days. This past August we moved into an off campus apartment together. We got a kitten in September and we're living together this summer and next year too, and hopefully for years to come.