Btice water buffalo horn is highly durable in the environment it is naturally from. Hot humid jungle. Especially compared to wood, horn resists mold/fungus much better in that hot humid jungle. Also since horn is rather porous, and the oils from the hand are rather nourishing. A knife/machete/khukri/bolo that is used every day, in that hot humid jungle, gets a tiny bit of protection every day.
Now flip over here to the US. Most of us dont live in a hot humid jungle, and even in some of the more humid places in the country, the humidity difference is rather large. Also, with many places having 4 seasons (or some semblance of), humidity/temp changes are much higher than the natural environment where the horn was originally intended. Finally those infected with too much HIKV, or just dont have enough things to chop, dont use the knife as much as it would normally be used in its native environment (eg. 24/7), so none of that lovely hand juice gets rubbed on regularly. Also, the humidity/temp change from Nepal, to dry arid Reno, and then to whatever customer is the final destination can be quite dramatic. And almost nothing likes drastic humidity/temp changes.
Anyways, as to whether the horn will ever settle. If you live in a 4 season area, it wont ever settle as nicely, as if you live in a place where things are constant. However, unlike most wood handles, since the horn isnt sealed (unless you sealed it with super-glue), most likely youll need to put something like mineral oil or lanolin, to prevent the massive escape of moisture, and help the piece deal with the constantly changin humidity/temp. Or you could put it in some kind of home-made humidor/storage box where temp/humidity is kept at a constant. Anyways, I rambled like I always do. Worst case secenario, once all the moisture runs out, youll have a few big cracks (though probably not as big as you may fear), realistically with a little maintenance nothing too bad.
I have a (oh wow I just realised its 25 years old now, it was bought a year before I was born) horn hilted bolo, that before I got it 14 years ago, was stored in a grill outside my parents home in Rochester, MN. And when not in that grill it was tortured through some pretty harsh gardening, which many would consider abuse, but back home is considered what a bolo is for. Its also been used as a fire stirrer, paint can opener, etc... Anyways, beyond getting washed off by the garden hose if too dirty to return to the leather sheath, it received no care. If youre not familiar with MN climate, well summer can get hot (and there were years where it topped 100, though not too often), and winters can get real cold (brrrr...negtive 30 degree cold). And that poor little bolo sat in that grill with no love. Anyways, the point of my story, is that despite all that neglect/abuse there is one semi-large crack down the hilt, and it thats about it. Cracks on horn are cosmetic, and unless that thing is cared for daily, or kept in some hermetically sealed container, or you are incredibly lucky to live in a place that never has any temp/humidity changes, they are inevitable.
Oh lordy, did I ramble.:footinmou