Doubles (i.e., ascending 2 climbs back-to-back) is a staple of training for routes. Stacking indoor climbs better simulates the length of outdoor climbs. Personally, I prefer climbing an easier route on the 1st lap and stepping up the difficulty on the 2nd lap. Thus, better treating one of my biggest personal limiters - executing consistently difficult moves in a prefatiged state.
Lately, I have been applying the same techniques to bouldering. I climb a problem, rest, and then climb the same problem again. During the rest period, I focus on improving the 2nd lap. My second ascent of a boulder is always more efficient.
This rapid, self-generated feedback has been catalyst for improving the quality of my climbing.
The mental pressure of getting to the top is lessen during the 2nd lap. I trick myself into putting the process before the outcome.
Since the primary goal is technique improvement, I stay as fresh as possible by resting almost completely, but not long (less than 2 minutes). I choose problems at my flash level or below.
Bouldering Doubles enable me to get a large volume, high quality movement in a session. The foundation for improvement in a skill-based sport.