its up to yourself, i have heard of people only sterilising for the first 6 weeks, sounds crazy i know, but some believe as long as you wash the bottles properly of course that not sterilising helps build up there amune system,
which is better for them later in toddler years,
i think i sterilised the whole time she had bottles!
tho im breast feeding this time round, but i have bought a couple of bottles and a single bottle steriliser! just seems safer to do so!