I wasn't very clear about it because it does really vary a lot. I've read of people reaching 40-50 in a week, for me it took me about 15 days.
After that I went 'cold turkey' and dropped QWERTY, while doing that I think that in about a month and a half I reached ~70 WPM.
In my experience it took around 1-2 months to become fully "fluent" in Colemak.
It took me about 3 weeks to acclimate to Dvorak, but I actually used a copy of Mavis Beacon to help with the transition (no joke.) I mean 80wpm. It felt both faster and more comfortable after that.