I would use his meals to hunt for his food or track him with it, it will wear him out mentally...higher drive WL's need mental exercise as well as physical.
What surfaces are you walking? If it is pavement, I'd change it up to sand/grass/hills etc.
Really, mental exercise will rock his world...obedience/tug/ obedience/perchwork(rear end awareness). I'd spend more time on that then going for walks to try to drain his energy.