With a little over 24 hours left on my mobile date period, I went over my 5GB limit. A non-desired Windows update not long ago helped that along quite a bit. My internet has slowed to a crawl.
Somewhat ironically, it was a manually initiated 76MB Firefox update that pushed me over the edge. It slowed tremendously about half way through and then failed after over an hour of slowly downloading. Apparently, Firefox downloads have to start from the beginning if they’re interrupted.