What age do babies not need to wear vests ?

Where does it not fit him? You can get vest extenders which make them a bit longer, I use them to go over the cloth nappies.

It's probably personal preference to when to stop wearing vests, I stopped about 18 months with my older one but could have probably stopped before. I guess when they are walking and not dragging their clothes around the floor it's not as necessary!

My baby need to wear bigger vests because he has a long torso and I bought vest extender clips on Amazon so we get a bit longer out of them. Don’t know if this would work for your boy? I think they need to keep wearing vests especially in the colder months until they are a bit older but not 100% sure as this is my first baby x

Theres no rule, are you using them to stop the nappy sagging? I started using vest and pants at 15months for my daughter. Its annoying having to strip all clothes to remove a vest! Much cheaper too, (half vest without poppers)

With my eldest, I used them up to size 2-3 which she was outgrowing anyway as we started potty training aged 2 years 2 months (she's very tall)! From potty training onwards, I just switched to normal children's vests and pants. I'm guessing he's outgrowing in width rather than length? Have you tried bigger made brands like Jojo Maman or M&S? I second the comment above to use vest extenders if it's a length issue which it was for us.