However, if practical considerations like time and money were of no concern, it's possible to cut down the casino's odds enough to make them feel uncomfortable. As long as you can continue to double down, you are extremely likely to eventually win (although it's possible that you could play once per second for 10,000 years and never win!). In practice, the problem is that you will either run into a max-bet limit set by the casino OR you will run out of money.
I once engaged in this strategy (using play money at a fun casino) by always betting on black, so that my chances of winning were 18/37 per spin. I started with enough money to continue doubling down even if I lost 5 times in a row, which had a probability of occurring of (19/37)^5 = 3.57%. I played all night and racked up quite a lot of cash, enough to get me to being able to sustain 6 losses in a row, which had a probability of occurring = 1.83%. Eventually, I lost it all because the improbable happened - I lost 7 times in a row, which had a probability = 0.94%!
By the way, if your base bet amount is b, the amount you would need to make one more double down bet after n consecutive losses is equal to 2^(n)*b. So if you want to be able to survive 1 loss and your base amount is $100, you need to have at least 2^1*100 = $200. if you want to be able to survive 7 losses in a row, you need to have a bankroll of 2^7*100 = $12,800. If you want to survive 15 losses in a row, you need 2^15*100 = $3,276,800.