At the beginning, my hair was seriously abused - I was about APL, but had extremely thin uneven hair, with split ends on pretty much every strand, and even all along the strand. I used to not moisturize it at all, and flat iron on wet hair!!
It took me about 6 months to get significant change - I just deep conditioned, stopped using heat, moisturized faithfully. That was it. But the ends of my hair were completely destroyed, so I had to cut them off after trying to nurse them back to health for the entire 6 months.
After the 6 months, my hair was much thicker, had minimal breakage and just better. But the heat damage was still there, so I had to cut again after another 6 months (so that's 2 cuts within a year) all the way to my nape.