Updating your All-in-One Revit Family ...
You should backup your Revit Projects as well as the All-in-One Families before updating.
Every All-in-One Revit Family comes with the actual Version as Prefix to clearly indicate the current Version of the All-in-One Revit Family:
|M / I
||Metric / Imperial
||Unique Family ID
If you want that the new Version updates all your previous Versions within your Revit Project, you would need to rename the Family within your Revit Project as the new updated version received prior to loading the updated Version. If you do not rename the previous Version, the new version will be loaded additionally rather then updating the previous Version you have in use.
(Released March 8th, 2011)