Culling and reparenting

If I reparent an object to another, does this immediately affect culling, or is the culling tree to some degree static?

To explain, I have a number of nodes that represent rooms in a side-scrolling 2D game. Objects are initially parented to a single root node, and are assigned to rooms after start-up, but on entering a room I reparent them to that room’s geometry NodePath. For culling purposes, in order that the culling system doesn’t find itself presented with too flat a culling hierarchy, I want objects that enter a new room to be culled with that room (presume for the purposes of this discussion that the room’s bounds fully encompass the object’s bounds) – will this happen automatically as a result of the reparenting, or is there more to be done?

I strongly suspect that it does happen automatically – it doesn’t seem to make much sense that it shouldn’t – but I want to check my conclusion on that.

As I understand it, a bounding sphere is generated at each level of hierarchy, that contains the bounds of all child nodes. If the parent is culled, then all child nodes are also automatically culled without needing to check them.

Yes. Bounding volumes are entirely automatic, unless you go out of your way to override this.