for tests while scaling the overclock higher and higher i do 10 minutes of priority 9 Blend test (i custom set it to do 3 minutes instead of 15 on each number to test). Once i think ive found my desired overclock, at least 3 hours on priority 10. some people will tell you 24 hours, but i prefer a combination of normal use (how long it takes X application to launch) and stress tests (play some games, run dolphin emulator, P95 doesnt always push the CPU in the same way as normal use will)