Even if the payout fluctuations with Thunderstruck are sometimes higher than with other Microgaming slots, you don't need to worry. Over a long period of time, the slot machine, the payout rate of which is specified by Microgaming, has to pay 96% back to the customer in each of the software manufacturer's partner casinos. These odds are monitored by independent organizations (at Microgaming casinos mostly eCOGRA).