Not so much spring life as cam life as any torsional movement is transmitted directly to the cam without the benefit of a chain or belt damping vibrations. The opposite is also true with a cam at super high revs transmitting harmonics to the crank. A really, really good harmonic damper is mandatory and balancing needs to be spot on as well. My machinist showed me an infrared video he took of a valve train on a spintron fixture at 8k and 9k when he had the Busch series contract. It's amazing what goes on. Everything seems to turn to rubber.
I've looked for a belt drive for the LA's and have been unsuccessful so far. I imagine it would also require an electric water pump.
