Assuming it's the same as on beta there's a "fast" section near the beginning and then it more or less keeps a pace, but may slow down further as things get higher and higher.
Colossus kits are at:
#1: 120, 360, 600, 720, 840, 960, 1080, 1200
#2: 1440, 1680, 1920, 2160, 2400, 2640...