The watchmakers here agree that especially the 7750 needs an immediate service, as soon as you get it. It's a complicated piece of machinery, and rep factories don't service them at all before selling them.
If you love, and plan to keep any mechanical rep ... service it. Wear it for 1 month .. then decide if you want to keep it "forever" .. and if you do, then have it serviced. Once every 5 years.
Let me add one small footnote .. if the rep is a cheap Asia21j movement .. wear it until it explodes .. then just have a new cheap Asia21j movement put in again.