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Krystle~Hime, if you trim only when you see split ends, I think then I just nailed your problem. Trimming only when you see ends means you're trimming not when your strands look like this:
Coz that horrible split is as tiny as 1/10 of this line -->
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...which you cannot see.
Even at this stage which is clearly the step before part of the hair breaks off, your eyes still cannot see because this image is a hair magnified 1000x:
So this is probably about 5 mm of a hair strand, which is not more than this __. So if such horrible damage is happening at such a small scale, surely by the time your eyes can easily see it, it's already traveled up along that center tear and probably broken off quite a lot. After all, how can those skinny pieces of an already skinny shaft of hair survive the elements. So your hair stays at the same length.
TBH, I personally think that everyone can at least make it to APL, even if their growth cycle is only two years...because they can achieve about 12 inches give or take.