I think I'd check the roots before I gave up on it, have you ever re-potted it in that 14 years?
Are roots protruding from the drainage holes?
When did you last change the compost/growing medium?
Do you use plant food?
I think I'd be inclined to either re-pot it into a larger pot (with fresh compost), or, prune the roots (remove about 1/4 to 1/3 of the old roots) and put it back into the same pot (with fresh compost).
I have a few bonsai trees (grown from seed or cuttings), I re-pot/root-prune them every couple of years, which keeps them healthy/vigorous and at a "compact" size...
Here are a couple of articles about the subject(s):
http://www.ehow.co.uk/how_6706628_repot-rubber-tree-plant.html
http://www.ehow.com/how_7761422_prune-ficus-roots.html
I hope this helps :) Neither of these "remedies" are going to bring overnight results, it's a case of "suck it and see" I'm afraid, but what have you got to lose?