Hugh:
I assume by now that all of the solvents used to dissolve the oil have evaporated and you are left with the linseed oil itself in the wood. As Jake said, the odor will persist until the volatile compounds also found in the oil escape into the air.
The curing of the so-called "drying" oils (linseed, tung, etc.) is based on cross-linking of the oil's fatty acids with oxygen "bridges" which eventually polymerize the oil into the dried finish. The "Japan dryer" helps increase the rate of these cross-linking reactions. Short of putting the piece in an atmosphere of higher oxygen levels, you might try to accelerate the cross-linking process by keeping the piece warm to help promote the cross-linking reactions. I don't think I would put it into an oven, however (the thought of a linseed scented roast is not very appealing!). Perhaps putting the piece in the sun to get warmed might be OK - although as I understand it, the cross-linking reactions are not light activated. You'd just be just warming the piece to help along the oxygen involved reactions, and promote evaporation of the volatile components.
Rob Wallace