Definitely not when special promotions are plenty around. Instead, you should consider buying, when dealers start to raise premium. Notice that they have done so, in the past two years; at the time when gold/silver price were almost exactly at the bottom for the year. Those were times when dealers lost the hedge (short position was really low), and price kept falling. And of course they had to rasie premium to protect themselves.
Within your buying window, purchase on the dip, be it quarterly, monthly, weekly, daily, hourly, or whenever; accumulation is the target. Occasionally you may choose to sell some of your premium metal at a profit, but always replace it with greater generic metal.
The premiums are actually about to go up on gold and silver american eagles. Dealers will have to pay 5% over now for gold eagles 1oz.
