You bet! If you notice that your pace is increasing at the same HR, or same pace and HR is dropping for a consistent period of time, say a few weeks. Then go ahead and retest. Usually I have athletes go at least three – four months before they retest. Also if you hit the 10% mark between aerobic and anaerobic thresholds remember that gap will not narrow further so you won’t need to retest for a while unless you have to stop training due to injury or life in general. Lastly, Aerobic threshold and AnT, like max HR will drop over the years as we age so you might want to check in annually to see if you need to make adjustments if you are training regularly. Hope this helps!