The shelf life of unrecorded media stored properly is about 10 years. TY media are on the low side of that figure because of the cyanine dye they use instead of phthalocyanine; but as long as they have been kept out of direct sunlight and away from heat, they should be OK.
Hey, I'm still using 8x-12x TY CD-R's from like 4-5 years ago and they all work just fine. It's the cheap stuff I'd worry about.