Most people just want to know about the latest & greatest.. most titanium frames are built to last a lifetime, for 90% of performance needs of the masses.
The ultra-lightweight, super thin-walled ti frames may save a few ounces, but you really need a reputable frame builder with lots of experience to ensure the durability doesn't get compromised during the welding process.
Personally, after riding different ti frames for nearly 3 decades, I can't say that there are significant contrast to the overall ride quality between modern vs older (10+ y-o) ti frames.
If you can find a used ti frame at significant lower price than a new one, likely it's going to last you longer than you can pedal without accidents.
More importantly, to know for yourself what you're looking for in a frame, what is your intended purpose & how much is your budget for your next frame?