Futures Liquidity Drying Up

One of the reasons that I have been transitioning toward longer-term trades is that liquidity in the futures markets has decreased by about 50% over the past 3-6 months. The Open Interest for crude oil has decreased by more than 50% in the past 4 months. The decrease in Open Interest for grains has been about 45% in the same period. As liquidity decreases and spreads widen, the only way to compensate, I believe, is to increase the length of time that a trade is open, permitting price trends to compensate for the decreased liquidity and widening spreads. I have also begun to concentrate more and more on futures with smaller margins.