I'm accumulated 1:120 gold to silver ratio, because I had the idea silver is undervalued and will rebound to 1:8

After studying the history of bimetallic standard, I'm no longer convinced this will happen. All central banks have settled on gold as the monometallic standard, and the ratio is unlikely to fall below 1:40 so long as banks only hold gold and no silver.

Now how much gold should one stack before it's too late?