After a lot of phone calls and emails I have finally come up with something on this one.
The Eastern Aero Marine, (who manufacture the EAM aviation lifejacket) Component Maintenance Manual states:
Life preservers removed from their packaging, functionally tested, inflated or deployed for demonstration or training purposes must undergo maintenance inspection before being returned to service regardless of their date of manufacture or "in service" status
So looks like my original suspicions were correct regarding these things. Good thing about the EAM jackets is that the pouch has the belly band sewn to the outside of it and also to the jacket which means it can be fastened around the waist. In an emergency, all that is required is to open the pouch and pull it over the head. Another good reson for people not tampering with them and re-packing themselves. For pilots who want to fly wearing a lifejacket the best option will be the horse collar type ie. RFD 11A or similar.