I feed my DD Seven to sleep. She is only 2 wks old though, but I love it. She doesn't like a dummy, and she can go to sleep in Daddy's arms, but she (and I) just prefer to breastfeed to sleep. At the end of the day, its your decision and if you are happy to continue doing it the way you are, good for you!
I will be quite happy to feed Seven to sleep as long as she wants to, but we are making sure that she recognises a couple of other ways to get to sleep as she gets older.