A new belt will outlast any rally, unless the design is consumer crap like using back of belt to drive water pumps. Belts were in use in F1 for a long time before they started being used on production cars. Belts are much lighter than chain, have better shock loading resistance and are quieter. Assuming the design is not a POS it's easy and quick to replace. Anything that needs an engine mount removed to do a belt change is a POS by definition.