From AaronWiki


This black rod carved of darkly stained wood is inset with religious symbols of various deities. Anyone who possesses the rod and is able to turn or rebuke undead gains four more uses of the ability per day.

Moderate necromancy; CL 10th; Craft Rod, Extra Turning, class ability to turn or rebuke undead; Price 7,500 gp.

Sage Advice

Notice that there are no charges per day, just a unclassfied bonus to the number of turns per day. Also note that you don't have to wield this rod, just possess it. The DMG states that bonuses from the same named source do not stack (except for Luck and some Cirsumstance's). The FAQ states:

"As long as you remember that the important number to track is not uses remaining, but uses expended, everything else should fall into place."

Given these facts our house rules are that Nightsticks do not stack, and owning more that one provides no benefit.