Never bought an Apple brand MP3 player though I've fixed a few and gave away one that was abandoned post repair
Did buy a SanDisk brand MP3 player (fraction of the price, small size, reliable and includes a Micro SD card slot in addition to the internal memory) many many years ago.
It has been through single-digit degree weather to being left in direct sunlight during peak hot Summer days and hasn't corrupted a single bit. It has crashed a few times over those years, (with no display,) meaning I only had to hold the power slide-switch to force it off and turn it back on. But that's it. Still works to this day. Never detected any issue with battery life.
To note, your whatever brand MP3 player is merely going to be treated like a file server. No reason to use that, versus a higher capacity USB Flash Drive or Bluetooth from phone.