Hello,
according to Mr. Stern's interview in the German magazine any Patek can be brought back to them - even after the warranty time - to adjust according PP standard. PP standard is -3 / +2 sek per day.
To be regulated, but to me 3 1/2 seconds is good going.
I would wait until either until the timing gets worse or the watch becomes due for a service.
After all the thought of having to send the watch to a service centre for a number for weeks, to me is quite a daunting prospect.

Hi,
I think this is a very good result and does not matter at all - considering it is on a winder.
Try it on your wrist and you may get a different result due to the different temperature and different positions considering day and night (I assume you wear it over night??).
I have a PP from 1963 which gains about 20 sec a day when it sits on my desk with face up - when I wear it day AND night it is within 1 sec. a day....
I would not send it for service and wait for months just for the small difference...
just my 2 cents
erich