M.H.
It just depends on when you want to. I think today's society puts to much emphasis on taking children's comfort items away to soon. And really how much different is a sippy cup vs. a bottle?
My son was off bottles by 10 months and at 3 still treats his sippy's like a bottle and is attached to them. I don't understand why you take them off the bottle only to have them latch onto something else!