One of the puzzles of the universe is a branding of used back-up tape as 'certified'. The idea being that a backup tape is like used tires and one can determine the expected life of the used product. The amazing part is the concept of storing backup data on used data tape. Now in the market they don't like to use the word 'used' but that is exactly what certified data tapes are and further their 'cheap' price is deceitful.
Many times we have priced tapes to find some amazing deals only to find out that they are actually the used data tapes. Very little information is provided on exactly what a 'certified tape' means. Nor is there any industry studies on the consequences of using such 'certified back up tapes'. One is simply buying a used tire with little or no tread left. Trust your back up data only to new back up tapes if you care about recovering your data.