How old is too old for a child to drink from a bottle?

The picture above is former video vixen and book author Kat Stacks, who shared this photo of her cute son drinking milk from a bottle on her  Instagram video.It immediately reminded me of  a special someone in my life that has refused to stop drinking from a bottle :-) @  1 year old and all tricks have and are still being used to change that, but I think most times kids grow out some things like drinking from the bottle with time and nurturing.
According to WebMD, allowing older children to drink from a bottle can lead to Baby Bottle Tooth Decay:

From WebMD:
Tooth decay in infants and very young children is often referred to as baby bottle tooth decay. Baby bottle tooth decay happens when sweetened liquids or those with natural sugars (like milk, formula, and fruit juice) cling to an infant’s teeth for a long time. Bacteria in the mouth thrive on this sugar and make acids that attack the teeth.
At risk are children whose pacifiers are frequently dipped in sugar or syrup. Giving an infant a sugary drink at nap time or nighttime is particularity harmful, as the flow of saliva decreases during sleep.
Although baby bottle tooth decay typically happens in the upper front teeth, other teeth may also be affected.
Think baby teeth are temporary, and therefore, not important? Think again. Baby teeth are necessary for chewing, speaking, and smiling. They also serve as placeholders for the adult teeth. If baby bottle tooth decay is left untreated, pain and infection can result. Severely decayed teeth may need to be removed.