It seemed that when the standard warranty was 5 years, I never lost a drive. Then they monkeyed around and went to 1 year, then to 3, and I lost about 5 drives during that time.
Warranties are an economic model based on statistics. You say you have A dollars to commit to paying for warranties, your product has an average failure rate of B time and cost C to fix, so you give D warranty. Your experience would say that they started making the drives with lower quality but didn't want to pay more for warranty work, so they lowered the warranty period.