Seems like we have several people here with some experience with spotlights.
Is there any way you can quantify how much light you need? You say you need it "for unlit areas beyond the parking lot to the bldg" for church lockup each night. If you could quantify it like "30-60 minutes of run time and a lot of light out to about half a mile" that would probably help. Then again, maybe I'm just being a little dense.
_________________________
"There is not a man of us who does not at times need a helping hand to be stretched out to him, and then shame upon him who will not stretch out the helping hand to his brother." -Theodore Roosevelt