How frequent should I change the bottle and teats for my lo? TIA...

To add on to what Hui Qun has written, if the bottle radiates a weird smell despite many washes, it's time to change bottles. This happened to my friend. She was using a bottle for over a month and it was pretty much brand new. Physically, there was nothing wrong with the bottle or teat but there was this odd smell (artificial and sour all at once) that wouldn't go after washing and sterilizing. So she tossed that bottle. It only happened to her that one time but reckon it's good to share.