Statefull PropertyDrawer

Is there a way to have an PropertyDrawer in Unity 4.2 that has an serialized state?

For example, I try to make a custom PropertyDrawer that contains a simple Foldout. My first approach of just storing a member variable in the PropertyDrawer failed for two reasons: First the same drawer instance is shared between all drawers of the inspector (means, if I unfold one property, ALL are unfolded). And second, the bool is not persisted and reset on every assembly reload.

Example code:

 [Serializable]
 class Example
 {
     public string bla;
     public string blub;
 }
 [CustomPropertyDrawer(typeof(Example))]
 public class Example : PropertyDrawer
 {
     bool foldout;
     public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
     {
         position.height = 16;
         if (foldout = EditorGUI.Foldout(position, foldout, new GUIContent(property.FindPropertyRelative("bla").stringValue)))
         {
             position.y += 16;
             EditorGUI.LabelField(position, new GUIContent(property.FindPropertyRelative("blub").stringValue));
         }
     }
     public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
     { return foldout ? 32 : 16; }
 }

Of course, I could put the "bool foldout" into the class Example, but I rather like to separate Editor-GUI stuff from my game data.

Is there any way of having a PropertyDrawer that holds some meta information without putting this information in the inspected type itself?