I took non cashable 600% bonus at betphoenix casino yesterday with 25x in playthru.  I bet big at the begining, $2 per spin, hope to win big and grind it out later.  I won up to $1k at one time and still won $500  when I had only $1500 left in playthru.  I hit nothing  since then, didnt matter if I changed different slots, I tried to play low variance slots, but it didnt matter, it just sucked out slowly my balance and finally I cashed out only $250.  I should have left the game when I still won at $500 and come back  a day or 2 later to complete the playthru (this strategy worked out for me before), but it's hard to do, I was thinking, only $1500 left in playthru, I get it done in 30 min, lol.   
has this ever happened to you when you are about to make playthru and your balance are gone right after?

what is your best strategy against it?

I hate this playthrough......so I never take a deposit bonus either. I want to withdraw any time...

I use to use bonuses all the time but I'm seriously thinking about not doing it anymore except on MG because I truly like the games and you can give up the bonus and cash out when you want and have enough.  Lock use to do that too.  They would remove the bonus liabilty once I made playthrough though and then I had no max cashout.

Now I can't remember which one it was but youre probably more familiar with MG than I am.. But I know it always shows Bonus and Cash balance so I assumed you can cashout and the bonus portion drops off.

My strategy:  I play roulette without a bonus.  I just tend to do well with roulette.

If I take a bonus, I play blackjack to "win a little." And then play favorite slots games.  This probably has a 20-25% success rate in reaching a cash out.  Though, I have to agree with the previous posts.  It SEEMS my bankroll just gets drained the last 10% of the playthrough!

I actually wished less people would take the bonus, so the casino's gets the answer the majority dont want there stupid bonuses cause it gives the house a huge advantage, and maybe we would see something better.

My strategy for casino playing is-
The casinos used to give you strategy cards to help you play.

I would tell you that if your level of play requires a strategy card, the BEST thing you can do is play CRAPS You are NOT ready to play Blackjack profitably.

Now, when you are ready, play very late at night. Mostly after 3-4 am. Try to find the most inexperienced dealer you can (slower game and less likely to run the shoe up). Play a hit & run strategy (get in, pop em for a couple of hundred and leave !) Go to a different casino and play there and attempt to repeat. NEVER play for longer than 30 minutes at a time. Move on.

$25 table works best in my opinion.

Hey Taaadaaa.  This is Realtime Gaming Software, right.  Here's something that has been working for me.  Are other games allowed on the bonus?  Play other games (other than slots), just one game, for the smallest amount possible, then return to the slots.