Some spells use touch attacks to deliver their effects to the target. For many of these (like shocking grasp), the touch attack is discharged the first such time that happens. These clearly fall under this rule here:
Holding the Charge: If you don't discharge the spell in the round when you cast the spell, you can hold the charge indefinitely. You can continue to make touch attacks round after round. If you touch anything or anyone while holding a charge, even unintentionally, the spell discharges. If you cast another spell, the touch spell dissipates. You can touch one friend as a standard action or up to six friends as a full-round action. Alternatively, you may make a normal unarmed attack (or an attack with a natural weapon) while holding a charge. In this case, you aren't considered armed and you provoke attacks of opportunity as normal for the attack. If your unarmed attack or natural weapon attack normally doesn't provoke attacks of opportunity, neither does this attack. If the attack hits, you deal normal damage for your unarmed attack or natural weapon and the spell discharges. If the attack misses, you are still holding the charge
Others have specific language about how they interact with combat. Elemental touch is one such spell:
You gain a melee touch attack causing 1d6 points of damage of that energy type, along with a special effect described below. You also deal energy damage and the related special effect when you attack with your hands using an unarmed strike, a single claw, or a single slam attack. This bonus damage can never apply to multiple weapons.
So my question involves spells that grant touch attacks over a duration without a discharge, like disable construct:
You can make a melee touch attack to send a pulse into the target, interfering with the magic that endows it with life.
(essentially, spells with range: touch that are some duration other than instantaneous without special language that explicitly outlines their behavior)
Can natural attacks be used to make "free" touch attacks with spells of this type, the same way as in the "Holding the Charge" clause (even if this isn't "holding" the charge, per se, since the spell is not instantaneous duration)? If so, can that happen only once per turn, or with every natural attack (if the creature has more than one)?