Is it advisable to extract the juice from the leaves with a juice extractor used for wheatgrass? How much to drink? How long will it stay in the refrigerator?
I don't think this will work, although you may prove me wrong.
Olive leaves are not "juicy", but rather leathery so I doubt the juicer will extract much.
If you do succeed it should last well in the refrigerator but you will have to try to find out how long.