I may sound ignorant.... but was wondering is it a must to sterilize baby's feeding bottles?

I would suggest to best continue sterilising your baby’s bottles until he/she turn at least a year old. Babies are vulnerable to the germs that cause diarrhoea and vomiting. These germs can develop very easily in milk. Bottles and teats have nooks and crannies that milk can collect in. Sterilising is the only way to ensure your baby's bottles are free from harmful bacteria. By the time your baby is one year old he/she will have started to produce his own antibodies and be more resistant to harmful germs. Hope it helps.