Magento turn off URL rewrites for invisible products

Question

I have my products made as "configurable products" and it's around 300 of them. And they have around 10-20 simple products associated (each). But 2 of my configurable products have around 3000 simples. So it is around 10.000 simple products that are set to 'not visible individually'. And of course magento creates for them url rewrites, and reindexing it takes too long. Is it possible to turn off url rewrites for 'not visible' products?