There's only one way to make five of a kind, and that's to have four aces and the bug card.  If you find yourself with that good fortune then your best play is to spit them so that you play a pair of aces in the 2nd high hand and three of a kind in the high hand.  There are just two exceptions to this:

1.  If you have four aces the bug and two kings, play the kings in the 2nd high hand and keep your five of a kind together.

2. If you are playing at a casino that offers a bonus prize for drawing five aces and requires that they be played as five of a kind to win the bonus prize.  Be aware of the house rules for promotions.  Nobody wants to miss out on a $50,000 bonus prize in order to win a $25 bet.