Magnetic tape cartridge group and magnetic recording and reproducing device

A magnetic tape cartridge group comprising:

• a plurality of magnetic tape cartridges in which a magnetic tape is wound around a cartridge reel and accommodated in the magnetic tape cartridge,
• wherein the magnetic tape includes a non-magnetic support, and a magnetic layer containing a ferromagnetic powder,
• the magnetic layer includes a plurality of servo bands,
• regarding 100 reels of magnetic tape cartridges in the magnetic tape cartridge group, in a case where a maximum value of an absolute value of a difference between a servo band spacing obtained before storage in an environment of a temperature of 32° C. and relative humidity of 55% and a servo band spacing obtained after storage in the environment for a storage time T is defined as A, a unit of A is μm, and T is set to 24 hours, 48 hours, 72 hours, 96 hours, or 120 hours, an arithmetic mean of medium lives calculated by a linear function of A and a logarithm loge T of T, that are derived from a value of A and a value of the logarithm loge T of T is 4 years or longer, and 3σ is 1 year or shorter, where σ is a standard deviation of the medium lives of the 100 reels of the magnetic tape cartridges,
• the medium life is T, in a case where A satisfies Equation 1:
• A=1.5−B, and (Equation 1)
• the B is a value calculated by multiplying a difference between a maximum value and a minimum value of servo band spacings obtained
• in each of the following five environments of
• a temperature of 16° C. and relative humidity of 20%,
• a temperature of 16° C. and relative humidity of 80%,
• a temperature of 26° C. and relative humidity of 80%,
• a temperature of 32° C. and relative humidity of 20%, and
• a temperature of 32° C. and relative humidity of 55%,
• by ½, and a unit is μm.