How long do sterile bottles really stay sterile?

[MindUtopia]

I have a Tommy Tippee electric steriliser and I know you can take out the bottles and quickly close them up to keep them sterile for when you need to make a bottle on the go, but how long do they really stay sterile for?

Since we switched from BM, I've been pre-making bottles in two batches a day (3 in the morning for the day feeds and then 3 in the evening for night and overnight feeds). But I just can't get over how rancid formula smells and tastes when it's not made fresh, so I've started sterilising the day bottles, putting the lid on right when I pull them out of the steriliser and then making bottles fresh during the day. But can they really stay sterile for 4-6 hours? So far, it seems fine and it hasn't caused my daughter any issues, but just curious. This steriliser is a bit of a faff, so there's no way I'm doing it every time I make a bottle.

 

[Ktothema]

Its claimed that its 24hrs, but that does depend on what type of bottles you have. Something like Dr Browns with big holes in the lids are not going to keep sterile for very long. If you're worried you could switch to cold water sterilising. We did this for a holiday when DD was young and never looked back.

 

[lilone2013]

I have a tommy tippee steam sterilizer I do it 2 times a day once all bottles are used I keep them in the sterilizer and I boil the kettle an hour before and I keep
The water in the bottles
For 6 hours and I add the powder just before a feed and shake well x