I don't doubt that, I had a bullmastiff cross pit that would run all day and even caught a few roos after a short burst. I bred his mum , the pit, 7 years later to a bulldog and the pups have no stamina. At 17 the pit/bullmastiff got into a fight with his bulldog/pit brother 10 and flogged his arse. I could imagine a bullmastiff lurcher having endless stamina.Pic of Bubba the pit/bullmastiff at 18, had to PTS about 6months later.