Are you sure something more is not going on. Something sounds very off. I mean the fact that you are splitting at such a rapid rate. Also, as hair grows out, the ends will naturally appear to be thinner. One overriding factor is that our hairs shed and are naturally going to be on a different growth schedule. With that, your ends will not always look as thick as they did when you first did a blunt cut; especially as hair gets very long. But if your hair is breaking off like you said, then maybe look into the methods out there that prevent splits like that. that is how I avoid trimming -- and jumped into the group of those that do not trim at all-- its works if you have found a technique that prevents splits in the first place.
I'm pretty sure it wasn't anything else because the only thing I changed on LHCF besides the not trimming is started to use moisture on my hair when I used to go bare. I started to moisturize my hair because it was preached ad nauseum on the forum (and by Cathy Howse that you had to keep your hair moisturized). So surely that shouldn't have caused my hair any damage. I was wearing it in braids as before and the pic you see of thin hair was me undoing a braid to redo and being horrified by how thin m hair felt.
I guess I can't convince you but I know myself that there isn't anything different I did except adopt the good habit of spritzing my hair with a moisturizer instead of letting it just stay bare and dry. I kept it braided so no manipulation. I just didn't trim it when I redid a braid as I always did.
When I went back to regularly trimming, even after a period of heat damage in 2004 when I had to do another major trim, my hair in 2006 was thick as it had been before:
My twist were full from base to ends:
And even my press looked really thick (and I have fine hair):
So maybe it seems hard to believe, but the proof is the pudding for me. And I usually examine all things before blaming one thing, and for me it was clear that not trimming regularly was to blame for my hair ends looking so bad. I mean, if it had been something else (products, health) surely it wouldn't just be the ends that were thin. Clearly by not trimming off the split ends, I just allowed them to continue to split further down the strand until they broke off. It's as clear as day to me.
In response to the bold, protective styling might help keep my ends from drying and splitting and might extend the time between dustings, but even those who protect will tell you that their hair splits. If you think about a strand it looks like a tube. The end is open. It's bound to lose moisture if exposed to the air even a bit, and friction against that end is just the beginning of trouble. I really think that everyone with really long full hair has to get a trim even when they protective style at one time or another. Wanakee was an advocate for this and she certainly knows what she's talking about. Those of us who don't PS just need to do it more often than not.
ETA To address the part in red: I didn't actually SEE my hair breaking, but what other explanation could there be for my ends looking thinner. They're not breaking coz clearly I still have more or less the length I had if not a touch more; they are just thinning badly to a very weak point that is obviously going to break off. Maybe the tips were breaking but not enough for me to notice any loss in length. What I did notice was how instead of having the fullness of the months before, tracing my hair from base to ends went from thick to almost invisible--something I had not witnessed on my head in 2 years. And because I'd been reading about the science of hair, I could only come up with one explanation, and I'm still 100% convinced I'm right.