Tony, I have used them for very short term while waiting on extra bungs and airlocks to arrive in the mail. In my opinion, the seal is not airtight and will not keep out bugs. It is a good thing to bulk age with bungs and airlocks so as to keep expelling CO2.
Better keep your sulphite level good and top up well!
I use them while keeping the carboys in temporary storage with some meta slurring at the bottom. Why spend all that money and time to "guess" for a good seal. I had thoughts about using them to "pressure rack to fill my bottles" but soon changed my mind on that as well.
Follow the previous comments of the masters, they have been there.
Yeah, that is a good idea, I was thinking of a way to test those "oranges thangs" by putting some air through one of the stems and see it it leaks. Kind of a "hairy" idea, mostly worried about the glass exploding..not worthy of the risk.