If you buy using your honest hard work based money to buy, any time is OK. If it comes through dowry etc., then on your wedding day or anniversary you need to respect the free gift and thus pray to Goddess Laxmi. GOD doe snot bless when you eat even on a leaf, but prayers and genuine offer of food – just the thought , gives you a peace of mind. Remember, our ancestors did not use metal plates, only earthen plates. I am sure you get offended because you think there is a Sastra for every thing, but a pure mind and a simple prayer and devotion before you do any thing is all that will give you a peace of mind and free you from guilt. Bless you inlasaws for giving that plate if it was a gift from them.Is there any ritual to be followed to start using silver plate to eat, silver tumbler to drink any other silver utensils?