Dummies are a hard thing, I used one for my DS1 and he used to have it with him all night, the thing is though i found that sometimes when they get a little older and rely on the dummie then when its not in their mouth and they want it but cant put it in there they cry for it.
I only ever gave my son a dummie when he was in bed not ever did he walk around the house with it or go out with it. especially when they can talk i definatly do not like it.
I think you just have to go with what you think it right and what works best.
good luck