Yes, some of the famous brand do monitor their watches in used narket. I can confirm from my own close fren who's got emailed from Rolex regarding the sale of a watch he recently acquired and thus, disallowing future allocation. Concurs by another fren's fren who also received similar email from Rolex.
How the catch flipper is simple. Search online sales post, cross match with serial number (serious mistake) AND also date of purchase/warranty. Not many Milgauss sold on one particular date.. All sales of Rolex are diligently recorded.
I personally has allocation from AP and they expect us to keep their watches for 5 years. Can't afford a lot AP, thus definitely keeping them for life. As for Rolex, the expect holding for 3 yrs, as in their official Rolex Certified Pre own certification programme. I hav not reach the privilege of getting my 1st Patek so i can't comment on this. Well, they said PP is for generation keepsake so maybe they expect us to keep for life 😁