DD stays over at my parents for a night probably every 4-6 weeks. She's still breastfeeding, sleeping in my bedroom and occasionally waking for night feeds but my parents and her have worked out their own groove too so it has never been an issue. She probably first went around 18 months? Can't quite remember! She loooooves staying at Grandma and Grandpa's, she sees them every few days so they are all very comfortable with eachother.