I have this watch in for overhaul and repairs including stem replacement. I have had this response below from watch maker and just wandering on your thoughts. Thought it might be interesting as it doesn't happen too often. I have also put a video on you tube of the watch changing date if anyone was interested.Girard Perregaux Gyromatic rapid date change - YouTube Thanks
"I have found that the watch has a broken Auto Mainspring, this is something very odd and cannot be picked up in doing a quote. (This is only the second Auto mainspring I have seen break in 24 years) Even while doing the Overhaul on the watch it is difficult to see and it was not until I had the watch back together that the problem showed i.e. would only run for about 15 hours. An Auto mainspring is designed to slip so as not to damage the Auto winding mechanism when the watch is fully wound. A broken Auto Spring will slip similar to how a functional mainspring does, however it will do it prematurely hence the depleted run time of the watch.The manufacturer will only supply a barrell complete (not just a mainspring) I am of the opinion that we offer the customer the barrell complete at our cost price $80- which would bring the total repair cost to $210-
Sorry for the problem but as you can see by the first two sentences it is something beyond reasonable control.
Let me know if you would like any more information"