I prefer that approach when sparring -- conserve your energy, let your opponent wear themselves out, then strike.

With men, I always look for that trickle of sweat at the temple -- men ALWAYS have that, woman are a bit more subjective. Bottom line, conserve your energy, make them strike & miss repeatedly. It takes twice as much energy to strike and miss, than to strike and hit.

This works very well with the untrained, color belts and junior black belts. Very few black belts are going to fall for this, unless they came from a belt mill (which is a lot of them).