The reason the Ti rails last longer is the titanium has a much higher resiliency. I it will still deflect a minor ammount, but it will return to its shape to a much higher degree than the cromo variants. If they made saddle rails out of tool-grade cromo, it wouldn't break, but the ride would be horrible from the rigidity.
Another approach could be a suspended seatpost. It would provide a means to dissipate the energy harmlessly.