If you're creating bullets or something, there are two common ways of destroying them.
One popular way is adding a FSM that has a timer on it, and after a sertain ammount of time, it destroys it self.
The other popular way is adding a border to your scene, and when the object
hits the border, its destroyed.
Or if the objects always collide with something like ground, walls or enemies you can always call a destroy function right after impact.
What are you making? It make's it much easier to give you some help
if you are a bit more specifik in your request.