Under the Lordship of Christ, your local church is in control of the decision about a missions focus. The field missionary has no independent authority over the decision. The circumstances may be a factor, but they don’t determine whether or not you can change a decision or direction in and of themselves.
Every strategic focus vision has a termination point. Every vision shifts a bit with time and experience and more information. It’s absolutely OK to routinely evaluate (at least on an annual basis) what progress is being made, how intermediate goals are being met (or not met), the effectiveness of the people and strategies involved, etc. When adjustments are called for, make them.
It’s possible that you will need to make a significant shift in defining the focus or change the focus completely. Have you ever dreaded saying, “no” to something, worried over the ramifications and what people might think? Then, when you actually do screw up the courage to say, “no”, almost immediately after it feels so good and right. Try to remember that feeling of relief and calm as you make the tough decision and begin informed all the principals involved of your changes. It will confirm to you how fitting and genuine is the decision to make the change.
Don’t be fickle; try to make sure that you’re doing it for the right reasons. If there is a pattern indicating a lack of commitment, then you should reevaluate your decision making process and try to move forward with stronger resolve the next time. Don’t quit a focus just because it is difficult or due to “lack of fruit”. If you’re doing the right things and your people in place are doing the right things and all for the right reasons and motivation, then let God take care of the results and faithfully persist.