If you're not interested in the games in the current Choice bundle then I believe you could purchase as a gift and redeem it on some future month.
Humble Choice plan begins when customer redeems gift. Humble Choice content changes every month, so content received depends on when the customer redeems the gift. Cannot use to obtain Humble Choice content from past months. Must be redeemed on a new or compatible Humble Choice plan.
Not sure if this code works for existing subscribers, but if it does then I think you could purchase as a gift and when you redeem it on your account it will add a 1 month credit. edit: New members only according to the banner on the front page.
PSA: Price increases coming into effect tomorrow.
Monthly plan increasing from $16.95 to $20.95
Annual plan increasing from $179 to $219.95
When i try to pay it says invalid coupon