Good question! Our carbonating bottles are made to withstand extreme pressure changes when used for carbonation, and since plastic degrades over time they sadly can't be used forever for carbonation.
Some Sparkly Tips:
1. Note the expiration date printed on the bottle and be sure to purchase new bottles as soon as the original bottles expire (you can still use the old bottles for still, bubble-free water).
2. The plastic bottles must also be replaced if put in the dishwasher (unless dish-washer safe), exposed to a heat source (50+ degrees), cold source like a freezer (0 degree or less), or if they have become scratched.
What's great is that all components of carbonating bottles except for the seal inside the cap are recyclable. Please check with your local recycling authority for more information on sustainable disposal options.