没有问题的，海关退税没有对退税物品是否被使用有明文规定，没有规定不可以那就是可以的。
海关的退税三前提为: 1. 非欧盟居民; 2. 签证时间少于三个月; 3. 购物后三个月之内退税。三个例外为：1. 在境内享受的服务（如车票，餐饮和住宿等）；2. 私人汽车零部件；3. 汽车的维护类（如加油和维修）。
海关规定详情：
Conditions
Under certain conditions the purchase of goods from retailers is free of sales tax:
1.You are a resident of a non-EU country and you are able to prove this to the vendor with your identity documents.
2.You do not have a residence permit that entitles you to reside in Germany for longer than 3 months, and
3.You export the goods yourself in your personal baggage within 3 months (that is, not later than the last day of the third month following the month in which you bought them). Your personal baggage is the property which you take with you, such as your carry-on baggage, or the objects in a vehicle you are travelling in, as well as the carry-on baggage you have checked in for a journey. Therefore any baggage that is sent either in advance or forwarded by post or by a forwarding agent does not meet this condition.
Exceptions
to tax-free shopping for travellers are:
1. services that have been rendered in Germany(it means that the price you pay for bus or train tickets, and restaurant or hotel bills, for example, includes German VAT),
2. goods for equipping private vehicles of any kind, such as bumpers, exterior mirrors, tow ropes, or first aid kits, and
3. goods for the supply or maintenance of a vehicle, such as fuel, oil, or care products.
信息来源自德国海关http://www.zoll.de/EN/Private-individuals/Travel/Leaving-Germany/Tax-free-shopping/tax-free-shopping.html

在欧洲买了手表马上戴是没有问题的，出境能不能退税的关键是你的退税手续有没有办齐全，退税单已经写好附上原小票，到了海关能给海关盖章审核就好，如果是名贵手表，海关多半会要求查看，所以把手表和保修卡一起放在身边准备好，就ok了。旅途愉快！