At the end of the day, does your ski still perform for you, as the ski softens, it may suit some people and be a little more forgiving than when it was new, if you have hit a slump that you cannot get out of, or you feel that the ski is less responsive you may consider that the ski is at fault, a difficult one, as change occurs, your body or technique will adjust accordingly and maybe difficult to detect a change until the ski is totally shot.
Lots of factors here, how you treat your ski, leave it in the sun or a hot car or put it in your bag damp/wet, may contribute to ski breakdown over time.
Somebody did explain to me that, when a ski breaks down, it can be good one day and not so good another day, went into some explanation about the fibres re-aligning, getting displaced and then re-aligning again, interesting but I do not know enough about carbon fibre to give a informed explanation.