Dr. Brown Bottles

Louis
So I have the Dr. Brown bottles that I used with my daughter, I've had a few people suggest I just replace the nipple and obviously sterilize the bottle to use for baby.... I've tried to find some information but does anyone know how long they "technically" say it's ok to use the bottle for? The bottles will be 5 years old so I'm just tempted to toss them & purchase all new.
Thanks!