you get your sneak attack on every attack you make that qualifies. The list of what you need to do to qualify is pretty clear, although it is lengthy.
SRD:
The rogue’s attack deals extra damage any time her target would be denied a Dexterity bonus to AC (whether the target actually has a Dexterity bonus or not), or when the rogue flanks her target. This extra damage is 1d6 at 1st level, and it increases by 1d6 every two rogue levels thereafter. Should the rogue score a critical hit with a sneak attack, this extra damage is not multiplied.
Ranged attacks can count as sneak attacks only if the target is within 30 feet.
A rogue can sneak attack only living creatures with discernible anatomies—undead, constructs, oozes, plants, and incorporeal creatures lack vital areas to attack. Any creature that is immune to critical hits is not vulnerable to sneak attacks. The rogue must be able to see the target well enough to pick out a vital spot and must be able to reach such a spot. A rogue cannot sneak attack while striking a creature with concealment or striking the limbs of a creature whose vitals are beyond reach.
So, if you have 100 attacks, and all 100 qualify, then they all get sneak attack damage. Even if they are in the same round, 5 rounds, or 100 rounds.
The only real exception are some spells and feats which grant multiple attacks with a single 'attack'. For those you only get it once, as with all precision based damage.
Following that, where is your writeup for the character?
