Hi,
I'm buying one of the above machines in anticipation of the arrival of my twins, and thought I'd stock up on filters for it too. I just wasn't sure if they had a use by date at all? I'm going to see what happens with breastfeeding, but I know that I will be formula feeding at some point - I did with DS from just before 6 months. So potentially they might not get used for 6 months. They don't go off at all do they?