Power output duty cycle - RB912UAG-5HPnD Vs R5SHPn

I am curious when I compare the TX output power of RB912UAG-5HPnD Vs R5SHPn 30dbm Vs 29dBm yet the 5HPnD has a big heatsink which would at first glance suggest it can sustain a higher power duty cycle, and where can i check and obtain this important information as there is no point is finding this out on a live network?