Dealership offered 100K warranty, worth it?

I recently bought a 2002 Discovery SD (36k miles) and it has the remainder of the factory warranty plus the certfied warranty which means I get about 19 more months of warranty. I am going to talk to the lady from the dealership today about extending the warranty out to 100K miles. What is a fair price for that type of warranty and is it worth it? Is there any haggle room on warranty prices or is teh standing price the only price. I know there are aftermarket warranties but if I spend the money I would prefer to get it through Land Rover.

I appreciate all input.