Running promotions to help Stake become bigger is good approach, especially when Stake has already a big site, and has good returns from their customers. It is likely a cycle of capital-investment-return-promotion, I like it. According to the important points that pointed out in your post, promotions should be run appropriately in order to have as much effective promotions as possible, and minimize leaks of promotion funds to cheaters. One more thing, I thought that it is always better to run long promotions with just acceptable payrates, not low, but not too high, rather than run short lasting promotions on massive channels, with highly payrates.
Their daily betting promotions and contest is working well for them, the reason they are doing it on a daily basis it has effects on their marketing strategy.
They have both short promotions the daily one, and long promotions the example was the race event.
there's none, everyone loves free money no matter what amounts, Free money is free money.. 
