The possibility to actually lose all of your money in that scenario is very little and you will most likely get the deposit bonus. You don't need to play x40 at once and get it, you can play anything, there is no restriction on your bets, you just have to wager x40 in total. So, if you deposit 0.5 and the x40 is 20 btc that means you can bet 10 satoshi on 90% for 200 million times, even tough you may lose a lot in there you will most probably not lose too much and will get that bonus after all.
Let say if your strategy work well, how much do you even left for that? To think that someone actually using this to get some profit is pretty useless thing. I do not say that it is not possible to do that, but with the time limit usually there is no way someone could achieve it, unless they are pretty lucky. And with 10 satoshi, how long do you think that it will work? 200mil bets is really long to get though
Sorry no offend on FJ but this is how the things works and it is your own choice to take it or not but a long term player usually do not bite this thing