Titanium may be fatiguable (is that a word?) but no one I know has ever had an issue with that. So while it might be within the realm of possibility, I'm betting my steel frame and all my friends' titanium frames will out last any carbon or aluminum bikes..... so that isn't something a normal sized person should be worrying about. We use titanium for its strength and lightness in airplanes... And THEY get a workout.