A 14 month old should be off the bottle for the most part now using sippy cups and finger foods.
I am a large supplier of plastic materials and additives to many industries in the US. NO plastic will last forever with the proper FDA properties not being compromised at some point. EX:multiple uses, dishwasher and handwashing over time will break down the properties causing discoloration, stickiness, etc. You should discontinue use and replace it. Cost wise its not that much $$ and not meant for 24/7 use.