At 12m when we moved to normal milk. Formula isn’t sterile in the uk (hence needing boiling water to make it up and kill the bacteria) so that’s why formula bottles need sterilising as it can grow hidden in valves and hidden bits of bottles. Milk is easier and you can just stick them in the dishwasher like a normal cup would xx
We stopped sterilising as soon as he was happily eating 2 meals a day and just made sure they got a really good scrub in hot soapy water when we do the washing up x
Formula bottles need sterilising until you no longer use formula, so 12m. Anything else doesn't need to be sterilised.
According to CDC no need to sterilise after 2 months with healthy baby
We initially stopped sterilising when we stopped using formula at 12 months. However the bottles started smelling a bit funny so we went back to sterilising!