My wife has purchased two watches from the "Giant Watch Sales" onboard ships.
The first was good. It was a Lucien Picard designer thing (the movement was probably Timex) and it ran for about three years until she broke it at work. Not many watches would have taken the bang it took.
The second watch was hilarious. She bought it in the shop and the next morning it was no longer running. We took it back to the shop and they first tried to find a battery for it. I told them I didn't want a battery I just wanted my onboard account credited. A 12 hour watch isn't a good thing. They did find another watch, and my wife did like how it looked so I agreed to take it. Well, this one lasted two days.
I took it back and this time they credited my account. It was a VERY good thing she bought the watch EARLY in the cruise.
She hasn't bought another watch on a cruise.