Four aces in Double Double Bonus — do you throw the fifth card?
Yes — discard it. Pat quad aces pay a flat 160; drawing one card for a 2, 3 or 4 kicker is worth 221.2766 per coin exactly, a gain of 61.28.
The exact numbers — A♥ A♦ A♣ A♠ 9♥
EVs are exact — every possible draw enumerated, not simulated — at max bet on 9/6 Double Double Bonus. Check it yourself: the analyzer runs the same solver in your browser.
See all 32 holds of this hand ranked →Why
Throwing a card away from a made four of a kind looks insane, and it is the defining play of the game. Twelve of the 47 unseen cards are a 2, 3 or 4, and each one turns a 160-coin hand into a 400-coin hand. You cannot lose the quad by drawing — the worst outcome is the 160 you already had. That is 12/47 of an extra 240 coins for free. This play does not exist in Jacks or Better, where every four of a kind pays 25 and the fifth card is irrelevant.
Chart line #3 of 39 — 'Four of a kind (draw for the kicker)'. Line #2 is the pat quad that already has its kicker; there is nothing to decide there. See the full solver-optimized strategy chart, or drill hands with exact-EV feedback until plays like this are automatic.