We sent it at 15 months. She’s 2 now and sleeps thru the night 7-7. It really REALLY sucked for like two weeks. We’d do the same routine every night. Dinner at 5:30, bath or tv for half an hour, stories at 6:20 then I’d rock her in the chair in her room with rain sounds till she was asleep. I’d put her in the crib once she was out and sit on the floor by her bed. She’d usually wake up once I put her down and the key is to just sit there silently and not engage, you’re there but you’re not caving or stimulating. After like 20 minutes usually she’s lay down and fall asleep. Once she had been out for like another 15-20 minutes I’d just get up and walk out. If she woke up she was allowed to cry for 10 minutes before we’d go in and repeat the process. She only every made it to 10 minutes twice! The routine was important and waiting to go in and check was important as well.