Washing baby bottles after every usage!

How old is your baby? When my baby before 6 month old I only wash with soap and use hot water to sterilise it in the morning. After each feed I will use a clean sponge with no soap just use water clean it up and use hot water rinse it. I follow the olden days method because too clean isn't good for baby too. Too much chemical not good for baby too. I feel nowadays kids immune system not very good comparing to our days that's why I follow my mom method how she brought me up is how I bring up my baby. And I believe what I did is right when my baby is down with 2 infection there were no fever at all. And she recover fast. When people at home is sick she isn't affected as well.

Personally we washed after every usage. Especially if you say the bottles are oily then the more the bottles should be washed and sterilized