That 'don't rotate your tires' thing is crap. I 'know' that's what it says on Sheldon Brown's site. He also says to not retire tires until cord is showing...on the front. Soooooooo....Let's say you still have some viable rubber on the rear. Rotate the tires, and you'll notice one thing, and that won't be a blowout. You'll notice some steering 'oddness' due to the flattened portion of the worn tire. You'll get used to it. The front will stay pretty much in whatever shape it's in since it was rotated from the back. Meanwhile...In time, the rear will begin to show wear, and I bet you this: you'll notice lower rolling resistance. Furthermore, I hereby posit that the 'myth' of aging tubulars for better performance is essentially correct, but it doesn't mean what is commonly understood and derided. Aging a tubular by using it on the bike wears down the rubber, thereby reducing the rolling resistance. The downside to this 'aging', and rotating your tires is pretty simple: more flats. I ALWAYS rotate my tires. I've NEVER had a blowout. Never. Not one. Oh, except for the overinflated brand new rear tire that was in the back of the car...and that was a pinched tube, the tire itself was fine.
Or, listen to everyone else, and chuck it. It's only money.
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Coach Bill