In blackjack, you should consider doubling down on soft hands those containing an ace counted as 11 mainly when you have a soft 13 through 18 against a dealer’s weak card (2 through 6). This strategy capitalizes on the potential to improve your hand while minimizing the risk since the ace provides flexibility. Doubling down is particularly advantageous with a soft 18 against a dealer's 2 to 6, as it gives you the chance to increase your winnings if you draw a strong card.