Similar to the OP, I buy discs, rip them, then store the physical copy for recovery purposes. I keep them in a box in the basement, the vast majority are still in working order. (Including discs purchased or burned 35 years ago.)

Like any other media, frequent use and handling will degrade discs, and sunlight is the natural enemy of anything plastic. The interior of a car will also get ridiculously hot on a sunny day, I have seen vinyl literally melt. (And crayons!) Actually I've lost more discs to theft than anything else, by a large margin.