Remember when battery life didn't suck? This is my beloved iPod's battery after playing on shuffle for 24 hours straight.
1. Add local files to your phone
2. Energy saving mode
3. Flight mode
4. Listen to music for forever
Bonus step: remember that laptops went black after 20 minutes in the good old days.
@OddDev
3 problems:
1) My phone doesn't have a headphone jack.
2) My phone doesn't have 512GB of storage.
2) Any modern phone is STILL going to die much sooner than "forever." There's no way it will last as long as this thing is going to.
@killyourfm Ah, you bought an iPhone didn't you?