My DD is 9 months old and we currently co sleep. Where she sleeps has always been changing based on her needs. When she was a tiny newborn we coslept because she wanted to nurse constantly and wouldn't let me put her down. We never planned on doing it, it just sort of happened but it worked out well and we were all able to get some rest. At 2.5 months we were able to move her to the cradle next to our bed and she started STTN in her cradle. At 4 months she started waking up in the MOTN for a feeding so I would bring her into bed with us when she woke up.
At 6 months we moved her to her crib in her own bedrooom and I would continue to bring her into our bed if she woke up in the MOTN. Now at 9 months she usually ends up in our bed somewhere between 10 and 11 at night even though she starts off the night in her crib. It works for us because I don't have to get my ass out of bed and if she wants to nurse I can just lay on my side, have her latch on, and then go back to sleep. Also, my DH and I both work fulltime and we kind of like having her sleep next to us all night. It's nice to be able to bond with her in this way since we can't be with her for most of the day. And we all sleep pretty well. Even when she is older and sleeping well in her own bed, we wouldn't be opposed to allowing her back in our bed if she is scared or sick and needs extra cuddles.