The slithering in the arches of my feet has not stopped for 3 years, not even for a minute. I just wiggle my feet continuously while sitting so I don't feel it happening. My calves are the same way and I just choose not to notice them. I also have twitches everywhere, but those don't worry me at all because I know they will stop after a few hours, days or weeks. Those don't seem like they happen as much anymore.
The way I figure it, if the continuous slithering, twitching in the arches were ALS, I would have severe weakness after 3 years. Even though it looks like atrophy in my feet, they don't necessarily feel weak. They hurt sometimes, but I can walk, run, etc. with no problems. Maybe they've always been boney, skinny feet, but I just never had a reason to look at them closely.
Anyway, the arches of my feet are my only concern. After all I know now, the twitches all over my body, do not concern me in the slightest. Those are classic BFS.
The good thing is, I don't worry about it anymore. I still research & visit forums, but I'm not at all bugged out or obsessed with it like I was the first 2 years. Even if it is ALS, it seems slow moving.
One thing I've neglected to mention is I had a back operation 7 years ago(Laminectomy Discectomy) on L-5, S-1 disc. It was sending severe pain & numbness into my feet, legs & buttox. It was BAD. I couldn't have lived with the pain much longer. This could very well be the root (nerve root that is, ha ha) of the problem.
Good luck to everybody.