Its not just significant magnetic field ( apparently we do have geo magnetic storms that corrupt data) it is that assigning the 1 /0 bit is not permanent. The 1 or 0 you store fades with time as it wants to lose its assigned magnetism. You might be fine for 10 years, or you might lose a critical bit corrupting a file. it is why archival experts suggest if it is critical data stored offline you need to store on two or more different mediums, because "1 copy is not a backup". Anyway, we are getting deep in the weeds of data entropy and recovery and I think your original comment was meant as being helpful to the lay-person...whom may not actually care to much if they lose a file or two, unless it is a crypto wallet key--i would trust those M series BluRay archival format since the laser alters the disk, but printing out on paper as another copy