I've read that a VBO (Vertex Buffer Object) essentially keeps a reference count, so that if the VBO's name is given to glDeleteBuffers(), it isn't truly dismissed if a living VAO (Vertex Array Object) still references it. This behavior is similar to "Smart Pointers" newer languages are increasingly adopting. But to what extent this is true and can be designed around, and if it applies to IBO (Index Buffer Object) as well, I haven't been able to find any information on.
If a VBO is kept alive by a VAO that references it and I don't intend to update it or use it beyond the VAO's death, I think the best play is to destroy my reference to it. Is it proper to do so? And can I do the same with an IBO?
Objects can be attached to other objects. So long as an object is attached to another object, the attached object will not actually be destroyed by calling glDelete*. It will be destroyed only after it is either unattached or the object it is attached to is destroyed as well.
This isn't really something to worry about all that much. If you glDelete* an object, you should not directly use that name again.