From what i gather as long as the watches, dvd's and games can be reasonably said to be for you then there is little that customs can do. But if you have enough of any to sell on, then you might have problems.
With watches, I tend not to bring back more then severn or eight at a time. But in the past i have brought more than this back.
Of course what you might consider you your own personal use, and what the customs officals do, varys quite considerably.
