I don't think that's okay. I fully wash all parts in between usage. My husband once left one in the baby's room and the next morning I opened it and it looked like some cottage cheese was starting
Do you need some additional bottles? I have some including a few with nipples that were never used. PM me if you want me to send them.
I'm a failed breastfeeder so I became a formula/bottle expert
Mama to B and E, Wife to E
Parenting with Hugs and Terror since 2011