Im so glad I came across this question as I have just started bubs on formula after he decided to ditch my boob. This is all new territory for us as I bf ds1 till he was 12 months. So, I decided not to sterilise, only cause he is 8 months old, and like party-of-five's bub, he licks the floor.... and shoes, and unwashed toys, and furniture, and practically everything else, so im pretty sure he has had his fair share of bugs! Plus my mum said its not necessary now, she's a midwife, so I guess I trust her advice. I also wash in boiling hot water, air dry and store in a clean container.