Contrary to popular belief, titanium is not as amazing as it's made out to be. It scratches really easily and loses its polished finish relatively quickly. I've had customers buy titanium rings from me and then complain when they get scratched. They don't seem to understand that titanium's benefits are in its strength to weight ratio, which is fantastic for jet turbine blades but pretty much completely useless when it comes to jewellery.
If we're talking about lasting forever, the closest thing is tungsten carbide. It is completely scratch proof. You can grind a tungsten ring on a rock and it will not have a single mark on it. Like everything it does have a downside and that is due to it's extreme hardness it is a brittle compound, if you drop it there's a chance it will chip or shatter.
