Belive it or not,greasing it will help to deteriorate the fibers. Keep it out of the sun as much as possable,and "wash" it every now and then to keep the dirt out of the fibers. Dirt is like sandpaper. Woolite is the best product to use. Hand wash in luke warm to cool water,hang in a shady spot to dry,out of direct sunlight. Also,if you know a furniture cleaner,there is an enzyme based product called,"Power burst" that is AWSOME on natural material's.
I know,I know,they didnt have Woolite back then,but they also didn't charge upward's of $200.00 for a woven bag either!