My opinion is that it's OK to continue to accumulate, or to start to do so, but don't go all in at these prices. Silver is a bit safer, and platinum is much more attractive right now.
My observations from the above chart are that when the price exceeded the 200dma by this much in 2006, it was then flat for a year before continuing a long rise. In 2008, it was followed by a “V” in price for more than a year, before continuing its rise.
In both instances, those who looked at the “overpriced” signal and kept on steadily buying did very nicely for themselves.