Are unity objects ID is static in project?

Hi Guys. I use "smallObject" for store something from project.

 public class checkResource : MonoBehaviour {
     public UnityEngine.Object smallObject;
     public string fileName = "Id.xml";
 }

I want to save a snapshot of this gameObject state. I save public unityengine.object Id to XML:

 " <resourceId>9230</resourceId>"

When I need to recover state, I load Id form xml and take object by his ID:

 ((checkResource)target).smallObject = EditorUtility.InstanceIDToObject(result.resourceId);

Can I'll be sure, that IDs in project will stay as constant.

Thank you.