Quote from IV_Trader:
is that the reason why broker(betonmarkets) is NOT offers bets with time < 8 days ?
Basically, yes. They were likely getting hurt on weekly bets from what I believe to be a lack of gamma/theta hedges. It's difficult to price to gamma. They went from 7d on index to 15d; now I have heard it's 10d?
The 7d lose approx 10% from first-day decay, not 15 as mentioned earlier.