Anyone know how long bottles stay sterile? I'm off to the Olympics tomorrow (woo hoo!) and my mum is babysitting I've got the expressed milk defrosting and would like to make up the bottles beforehand so everything is ready to go (DM is a bit ditzy so would prefer to do it for her). If I sterilise them in my steam microwave steriliser tomorrow morning, will they be ok at bedtime (7pm)?