I can make a prediction..... it will go on for a few months ....until they reached their goal for the new memberships and then it will stop. It is not sustainable to run bonuses like this for extended periods.... so they will possibly reduce the percentage or stop it completely.  

The Free spins on "Book of Dead" and "Gates of Olympus" is not really a "carrot" for most of the older gamblers, because we know the popular slots are being swept clean by the paid streamers every day.