Both aluminum alloy and hard steel sprockets will last the same amount of time when you keep the chain within 0-2% of it's original pitch.
Only when the chain grows from wear, does the sprocket teeth on any sprocket start to deform.
Hard steel/titanium/etc...sprockets only mask a chain that has grown past safe running specifications. The hardened sprocket can withstand a chain that has grown to unsafe lengths. The aluminum will start to show wear and let you know when you are running a time-bomb chain, if measuring the chain isn't in your schedule.
I know you will get suggestions to go to the hardest sprocket you can find, but that is simply a conventional wisdom bandaid at best. It does NOT address the problem that causes the teeth to wear in the first place...which is an elongated chain. Actually, since the hard sprocket teeth resist any sort of deformation, they can actually acclerate the wearing of the chain.
Are Renthals worth the extra moeny? No, there are better aluminum sprockets, for cheaper, available. Renthal has elevated it's prices on it's name alone.