yes, why not. immortality isnt bad thing right?
Consider it a flag. It is not known what result this decision will lead to. It can either save someone in the future, or lead to negative consequences.
If you have read to the end of the current version, you may have noticed how the purchased trinket helped in a certain situation. If I explain in more detail, it will turn out to be a spoiler)
Also, there we have is very low possibility that Cari himself did not come up with why he offered this to us :D