I think there is a tendency to want to establish predictable patterns - for example : " if I search X number of boxes of (fill in the blank) I should find X number of silvers " this is a false premise ,as it neglects the dominant factor- namely the random element ! There is no way of predicting when and where the " unknowing and (or) uncaring will put silver (for example) back into circulation . There also is no way to ascertain how often re- rolling centers are culling silvers . All of this to say- do what you can ,when you can -as long as you enjoy it ! You can't take it with you ,and "where your heart is , there your treasure is also ".