My girl is 3 and she stays in her room most nights but she is more then welcome to crawl in bed with us anytime. She was in our bed every night until she decided on her own to sleep in her own bed when we moved a few months ago.
never coslept because I didn't want to deal with trying to move him into his own room and thinking that I would wake up with a kid in my bed...a cousin of mine did that with her 2 boys and the boys still slept in her bed at the age of 10...I really don't see how cosleeping works at all
I coslept until my girl was abotu 6 mos. then I transitioned her to her crib so that we could have a choice. Some nights I bring her back to our bed when she needs additonal soothing but for the most part she nows enjoys her independance in her own sleeping space.