Magnetic tape cartridge and magnetic recording and reproducing device

A magnetic tape cartridge comprising:

• a magnetic tape which 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,
• in a case where storage in an environment of a temperature of 23° C. and relative humidity of 50% for 12 hours and storage in an environment of a temperature of 32° C. and relative humidity of 55% for 12 hours are defined as one cycle, a maximum value of an absolute value of a difference between a servo band spacing obtained before the storage and a servo band spacing obtained after the storage of N cycles is defined as A, a unit of A is μm, and N is set to 1, 2, 3, 4, or 5, a medium life calculated by a linear function of A and a logarithm logeT of T, that are derived from a value of A and a value of the logarithm logeT of total storage time T of the storage of N cycles is 3 years or longer, the medium life is T, in a case where A satisfies Equation a:
• A=1.5−B, and (Equation a)
• the B is a value calculated by multiplying a difference between a maximum value and a minimum value of the 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 32° C. and relative humidity of 55%,
• by ½, and the unit is μm.