Van Nics policy, I have not read it all but looks reasonable.
WARRANTY CONDITIONS
Article 1 – Warranty Period
1.1 Van Nicholas will replace (not repair) any Titanium frame that fails due to manufacturer defects in materials or workmanship for the lifetime of the frame. Every bicycle has a limited life, the so-called useable life-cycle. The duration of the useable life-cycle of bicycles depends on the type of frame, the way in which and the circumstances under which the bicycle is ridden and the care/maintenance the bicycle receives. The lifetime guarantee period is established on the basis of the duration of the useable life cycle of the bicycle. Van Nicholas sets the lifetime of their frames at an average of 25 years.
25 years is unusually long for a ti manufacturer. I was looking at this the other day. Enigma I think is 10 years.
Some manufacturers (Litespeed) have warranties for the lifetime of the frame. In other words, when the warranty lasts until the frame breaks – an internet search on their warranty issues will highlight those issues.
Kinesis UK is not a manufacturer but really just a sticker company. They commission open mold frames and components from Taiwan/China and stick their name on them. Basically if you buy a Ti frame through them you would get pretty much the same frame as if you bought directly from a Chinese company on aliexpress. The only advantage is if you get a dud frame immediately then you’re more likely to get a speedy response from Kinesis – the extra you pay is for them to accept the risk of returns plus to cover their margins.
I’ve had a Lynskey frame now for about 3 years. To be honest, were to go back in time then instead I would get a cheaper, lighter and stiffer carbon frame instead directly from one of the China manufacturers such as Hongfu, Dongfu or Carbonda. They’re using the same manufacturing processes for carbon as say Trek, who often use the same factories. Online reviews I’ve seen about them on other forums or on YouTube seem to be really good. You’ll get a lighter carbon frame from them for less than half the price of a Ti frame – so even if it is a dud and you need a replacement then you’re still quids in.
And no, Ti frames do not necessarily last longer than Carbon. Ti withstand scratches better, that’s about it. But a small imperfection during Ti manufacturing might only might develop to a crack many years later, after warranty periods end. So the infinite fatigue life of Ti is only theoretical.