Cert tests are typically run in shorter cycles, so I seriously doubt anyone runs 100 hr at one time.
However, in principle Gulfstreamaviator's right. I've mentioned before that I've conducted ground runs - routinely operating at various T/O ratings, 30 minutes or more at a time continuously above MCT. My conclusion is that extended time at T/O is not a safety issue, so 5 min. vs. 10 min. isn't a factor - EXCEPT in the regulator's eyes.
However, extended time at T/O is an economic issue, and performance deterioration (increased fuel burn, etc.) is aggravated by holding T/O longer than necessary for the mission.