Thanks for the advice. Unfortunately, this is not due to a bad utilisation of the cable. I make all my cables last as long as possible, and even my 6 year-old Macbook Pro charging cable is perfectly fine!
A goodwill gesture from Apple would have been appreciated, especially in this risky situation...
Edit: by the way, according to a european consumer law, every product bought within EU includes a 2-year warranty. It doesn't precise if it covers the device itself or the accessories as well. Thus, the cable should be covered by this law, shouldn't it?