Breast milk storage question

Kelsey
I know they say to follow the rule of 6's or 8's depending for breast milk storage. My question is, if it's 6 days in the fridge with a storage bottle...does anyone know how long you can store the bottle with nipple and dome cap in the fridge?  
I would like to pump directly into the avent bottles I have to feed with. Do I need to get the storage lids for milk that will be used the next day or would it be okay in the fridge that way?