We were told a year but now Joseph is one I have continued to sterilise his bottles and will do for as long as we are using them and formula milk.
We were told that the risks of not sterilising are small but I prefer to do as much as possible to avoid them. But again, Joseph crawls around the floor and picks up lots of things and at playgroup the babies all play with the same toys and have the chance of picking up bugs that way.
We were told it was to avoid things like sickness and diahorria, salmonella and Enterobacter sakazakii, which I just had to look up to spell and found this link https://www.nhs.uk/Planners/birthtofive/Pages/Bottlefeedingbasics.aspx