Fruit

The value of long-term missions, especially cross-cultural missions, is the fruit it can produce. Time and investment are key. Not just marking time, nor the investment of money. These things produce their own fruit, but they are not spiritual, nor do they always further God's kingdom. I'm talking about the time it takes to invest in people and God's mission, which will always extend God's kingdom. 

It's not rocket-science, as they say, it's obvious. It's what Jesus did when establishing the Kingdom of God on earth. He invested His time in people—twelve men in particular, three men more deeply (Mark 1:14-20; 3:13-19). This same model works today, but is not always followed. Why? Because it requires commitment, faithfulness, persistence, and other such qualities and disciplines not so popular in our current age.