HOT SPRINGS, Ark. – Like death and taxes, one of the certainties of our existence is that on the Monday preceding a Saturday stakes race, Steve Asmussen will work his horses an easy half-mile in something like 51 and change for their final tune-up. So on Monday morning, just after the renovation break at Oaklawn, his colt Chasing Time hit right on cue, a half-mile in 51.20 seconds under the supervision of assistant Darren Fleming while readying for Saturday’s Grade 1, $1.25 million Arkansas Derby.