Regarding the “foreverness” of titanium. Sometimes welds break. The most forever bike is the one that comes with a lifetime warranty with a good company backing it.
That said, I had a Litespeed that I rode for almost 20 years. None of my welds broke. I really enjoyed that bike but I did move on to lighter carbon bikes and they did have a little bit more of a wow factor.
In durability, Ti excels in the whoops department. Minor falls that could damage carbon won’t even faze Ti. With the right finish, you can also refinish your titanium bike over and over, making it look new again.
FWIW, carbon bikes can also be repaired relatively cheaply unless you’ve really mangled the frame.