In my case, when I fell from x100 to x50, after about a week I am not able to maintain it x50
(about 9,000,000 points per 24 hours)
Yea, speed-up it's practically over after you lose x100 speed-up But you still get x50 speed-up for 24 hours from time to time I think about speed-up as about tool to make it possible for little players to catch up with bigger players. Not something everyone should have for ever.