The lifetime warranty is for the original purchaser.
Quote from the q&a from there website.
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Q: What is the KONI warranty? How do I go about
getting replacements?
A: The KONI warranty is a lifetime warranty to the original
purchaser against defects in materials and workmanship
and against wear out for as long as you own that car
registered for street use. The warranty does not cover
damage to the parts caused by misuse, misapplication,
installation, motorsports, etc. If you determine you have a
defective damper you can either contact the company
which you purchased the unit(s) from or contact KONI
North America directly at
warranty@koni-na.com or
859-586-4100. To process your warranty, we will require a
copy of the purchase receipt and a vehicle registration.
We will generate a return goods authorization (RGA) and
can replace the dampers in advance at your discretion.
For more specific information about the warranty see
inside back cover