Lissa said:
Is it possible to never dry up completely?
yes.
your boobs keep producing milk for as long as their in use. There are cases of grandmothers nursing their grandkids in some isolated villages - keep in mind that in some places in the world people aren't so uptight about hygiene and propiety: for instance, in a village where a baby might sometimes get fed by a friend of the family who's lactating... why not? it's gross, but not unsafe.
I've read of women who give milk to milk-banks for years after their own children wean off the breast - I've read of women who gave milk to milk-banks when their own child died in labour - firstly as a way to ease the swelling without wasting the milk, and then as a way to stay connected to their unliving child....
a good book is "fresh milk" - a fascinating book of breast feeding stories - including one hawaiian man who took to comforting his screaming, hungry daughter with his own nipple while waiting for mum to come home - and in the end his nipples actually started to produce some 'stuff'... not milk, but... stuff.