Our daughter sleeps in bed with us, when should it end?

She is 6 months old. When she initially goes to sleep we put her in her crib. If she cries soon after we let her cry it out. Later in the night when she gets up I go get her and snuggle her back to sleep in our bed. This is on the nights that my step daughter isn't with us. When she stays over we don't put the baby in her crib at all so that the 4 year old can sleep (they share a room) This makes it impossible to create a schedule for the baby to get her used to only sleeping in her crib. Anyway, I like having her with us. She goes to bed early enough that we have time together for movies, , talking, etc. By the time I get her my husband is asleep so that he can be well rested for work. It works for us very well right now, but I don't want it to continue forever.