In an ideal world we'd be able to trust the manufacturer's quality control and all new watches would be free of defects, but in reality even brand new watches can and do have issues from time to time.
Do you have checklist (actual or just mental) that you go through when inspecting a new watch at an AD before completing the purchase?
E.g. checking for alignment issues (indices, day/date wheel, chapter ring etc.), blemishes on the dial, making sure the date changes over properly, that it winds smoothly, that any complications work properly, that the bracelet or straps are free of defects.
It's a little tedious to do this in-store, but much better than receiving a watch and only realising 2 weeks later that there's a piece of dirt on date wheel on the "17", for example. A defect found after a few weeks of ownership could lead to you being without your new watch while the AD addresses the issue.