I would think that if it were a limited timeframe group build, then it would be up to the original creator to indicate that it is closed to further entries. That being said, there doesn't seem to be any way to do this without deleting the group (and thereby losing all the entries). Perhaps a simple flag that can be placed on the home page of the group indicating that it's closed.

As far as maniacal, never crossed my mind Cricket (@bikequeen). The whole point of this site is to share our work and we all love what you are doing.

All is excellent with your entries, my friend @bikequeen! No timeframe in this GB, you may enter as many builds as you like here. In fact, the more you enter the better! Our Motorcycles GB would be lesser without your superb entries! Thank you for this and keep them coming!