這個問題比較複雜，需要經驗和市場重大event的了解

For example, you may want to consider end of Aug option due to the most important earning from nVidia which will pretty much set the direction for QQQ, plus VIX is coming down now so put option is not as expensive as when VIX was 60

Or you can extend it to Sept around Fed meeting, just in case Fed decides to F'up the market.

Over time, you will develop your strategy.