Ti will last a long time if done the way its supposed to be done.
You need shielding gas on both sides and usually a trailing sled with shielding gas.
Needs to be clean, rods have to be degreased, tubes too. Needs to grab new unused gloves for every job when welding. Hardmetal tools for chamfering (no sandpaper drums etc), stainless/better brushes to not contaminate and so on. All this has been known for at least 50 years. You want to avoid skin fat on the tubes and rods, and avoid oxygen/nitrogen in the material, because then it turns brittle.

The good builders does all of this for steel too. Thats why a good custom steel frame cost just as much (or very close to it) as a ti one. It takes just as long to build it to the same quality.

I think the reason we see complaints about ti durability is because some makers sometimes cut corners to save time. And you cant do that with ti. Then it will only last for maybe a few years or less.
Also some makers do weird "fashion" designs that would have failed even if it was made out of unobtainium. But you can hardly blame the material for this.

Also everything built as light as possible will fail sooner than beefier stuff. Surprise surprise.
Only like 10 years ago most people understood that. Those were race day machines, used for racing only. Race day machines last a season or 2. And then you get a new one.

I have 2 lynskeys and these are from the cheap end of the spectrum for ti. But I bought models with sane construction, tried and proven. Not anything weird dropouts or similar. I kinda doubt they will fail anytime soon.