Titanium frames do crack, so for me a decent, as in minimum 10 years, warranty is essential. I personally think its still worthwhile though for the ride quality.
Lynskey make an aweful lot of frames for themselves and other brands which might explain the jibes about them cracking. My lynskey On One cracked but was repaired as new. Excellent customer service from both Lynskey and Planet-x (surprisingly) as well. I’d happily get another.
Litespeed do seem to have a reputation for terrible customer service though.
Kinesis frames only come with a 3 year warranty, so i’d not buy another on that basis. I have a Tripster and its worrying that some are failing after 2-3 years (albeit for high mileage users).
Van Nicholas have an excellent lifetime warranty, but their designs are a bit limited at times (sorry Scotroutes 😉 ).