What is this lifetime guaranty about?
Our goal is that your devices can last and work as long as possible.
Therefore iFixit grants a lifetime guarantee on its spare parts for smartphones, tablets and Mac computers (excluding batteries).
Batteries are warranted for a total of 2 years.
On the following site you can read everything about this guaranty:
https://eustore.ifixit.com/en/Warranty/
https://eustore.ifixit.com/en/Warranty/