Personally - as its a comfort thing, I think it should be up to the child when they see fit to no longer have a 'pacifier'.
I sucked on my fingers until I was 8 - and was made to stop. So I remember it very well and I remember what it was like to have that comfort and then to no longer have that. It is not something you can ever get back.
This never caused any problems to my teeth or speech. The whole teeth thing doesn't have much standing in my opinion. The only teeth problems I have seen on dummy users are ones that use very cheap non-orthodontic dummies. I didn't mind splashing out a bit of money for a decent dummy for my child to suck on. They look better too - not that that should matter...but I never got buying the clearly cheap ones at the pound shop.
I gave my son a dummy as he was a sucky baby - he couldn't find his fingers lol! (and he didn't milk either!)... Mostly he used it for sleepy times, but when he was teething he wanted it more often. So, as it was a comfort thing for him, I felt it was up to him when to give it up. He did of course - shortly after turning two ...perhaps this also coincided with the fact he had all of his teeth then - but he got his teeth fast, not all children have them all at two. His choice, no coercion - 100% up to him.
After having a 10 and half pound son who was not fat but just really long at birth and kept up with his size (everyone thought he was 5 at 2! lol) - I know you really can't judge a childs age based on their size either. My friend has the opposite - her DS is a year old but still in 3-6 month clothing! hehe
Bottles...well...we can't all be perfect
lmao...But I wouldnt bat an eyelid at a 6 year old breastfeeding, so why should a bottle be any different? (I only cringe at juice and or coke, etc in a bottle...don't get me started lol)