Using Tommee Tippee and replace teets after 2 months and bottles after 4 months or earlier if they change colour (happens sometimes as I put them in the dishwasher).
Added: have always a couple of bottles in use so don't sterilize them as often per day as you do.
<em>edited by Kermi on 06/08/2012</em>
Im using medella bottles along with nuk nipples. Does anyone have any idea how long these can be continuously used? I sterilize each of them at least 6 times a day and have been using them for close to two months now.