Every parent seems to be so different, I have to say though...I have only had one parent who was quite picky about it being a glass bottle and she wanted to take the bottle home every night and wash herself (bring back every am) that was ok with me, thats what she wanted. Personally though, I ask the parents to bring extra formula or breast milk frozen and I prepare it as the child needs it then I keep the bottles at my house. I find that easier, there have been times the parent has forgotten things in the am such as food, bottle...that is not a good situation to be in when you have a screaming hungry baby and no food. I always store extras of everything (clothes, diapers, wipes...baby food, formula and bottles) when I need more I give the parent about a week advance notice in time to restock. (my motto is to do what makes it easier on the parent) when they come through my door in the am they bring ONLY their child, not a plethera of things.