Here is a quote from the Qt-developer forum: "Only the first application startup will be slow, since that has to populate the cache. All further apps start faster." This means that the Qt runtime libraries must first be loaded into the cache, but are then still available for other apps. I hope that explains things.
Sorry for that, Ableton can't do much, and we can't do much to speed up Live, when it is started after Windows reboot. The question still remains why Live is doing these scans at startup, which makes the situation even more problematic.
My latest test: (script does minimal changes)
Live start after full reboot: 4 min
Live start after starting it once before: 15 sec
I'm out on that problem-solving. It's a mess.