As noted in the Mind Techniques Guide duration of effects, either up or down, are dictated by RES check, Mastered ENR burning and Technique level. As buffs are considered consensual, the RES check component is not applicable.
The relevant passage:
Mundane: 1 Turn Full Effect / 1 Turn Reduced
Honed: 4 Turns Full Effect / 2 Turn Reduced
Epic: 6 Turns Full Effect / 3 Turns Reduced