Are extended warranties necessary on plasmas?

I was considering purchasing a 42 inch plasma last week for around $2000. The salesman strongly recommeded the extended warranty, at a cost of $500. I backed off because something seemed very wrong with a 25% markup for a warranty. The unit came with a 90 day warranty for labor and 1 year for parts. Has anyone had or seen any lemons that tanked out before the manufacturers warranty expired? Has anyone ever have a plasma repaired? If so, what was the cost?