In time, my friend. Every apple cable I've had has failed after a few years. Usually the sheath by the end will get squeezed off of the insulation and expose the wiring. Over time this gets damaged and eventually the cord stops working. Typically I would fix this with a layer of gaffer tape if I notice the cord starting to slip out of it's shielding.
There's also something about the wiring material that makes it prone to breaking the insulation at the mid point. Small pinches turn into a crack that becomes a gaping hole, and can also be a point of failure. Most of my old magsafe cables that have seen years of service look like zebras with all the black gaffer tape patches I've had to put on them, but they work at least.
Here are some images of this, it seemed to have become a serious issue when apple switched to that grippy rubber coating on their cabling:
Inspect your apple cables once a month for any signs of damage or pulling at the ends. Until Apple changes the material for their wiring insulation and beefs up strain relief at both ends, it's not a matter of if your cable will fail, but when. You can prolong this with patches of gaffer tape, but it will look like hell.
There's also something about the wiring material that makes it prone to breaking the insulation at the mid point. Small pinches turn into a crack that becomes a gaping hole, and can also be a point of failure. Most of my old magsafe cables that have seen years of service look like zebras with all the black gaffer tape patches I've had to put on them, but they work at least.
Here are some images of this, it seemed to have become a serious issue when apple switched to that grippy rubber coating on their cabling:
https://www.mobilefun.co.uk/blog/wp-content/uploads/2017/02/...
https://media.treehugger.com/assets/images/2012/10/FYGXC4BGR...
https://brokenapplecords.files.wordpress.com/2015/06/wave-3-...
This one isn't broken yet but showing some of the first symptoms:
https://i.insider.com/5cc1cac5d1a2f83ea64c99ea?width=1200&fo...
Inspect your apple cables once a month for any signs of damage or pulling at the ends. Until Apple changes the material for their wiring insulation and beefs up strain relief at both ends, it's not a matter of if your cable will fail, but when. You can prolong this with patches of gaffer tape, but it will look like hell.