Unfortunately, there's no way to answer that without knowing the future volatility. If gold stocks close higher every day, you'll actually do better than double. As we all know, markets don't act that way for very long. Even in an uptrend there are a lot of down days & every down day will take a bite because of the daily rejig. These things started trading in June 07 - since then HGU is down 45% even though XGD (the old-fashioned non leveraged gold stock ETF) is up 20%. As for the flip side, if you shorted XGD you'd be down the 20%, but if you bought HGD instead, you'd be down 96% - talk about your portfolio killers!

Here's what you could do - don't worry about the length of time, just sell when the short term uptrend (since Feb 5) breaks. Perhaps you'll be lucky and it runs up for a few more days, but you'll probably want to avoid holding during pullbacks.