About one month (going cold turkey). Supposedly it's more efficient than the two. It certainly feels less strenuous than QWERTY.
I am fearful of switching because of all the keyboard shortcuts I'd have to relearn. Sometimes an established layout like Dvorak and Colemak has scripts/modifications readily available from the community that can help you to get things working quickly, for e.g. Emacs and Vim rebindings.
How are you finding the keyboard shortcuts after your transition?
Is there any community around QFMLWY (forums/mailing list)?
The keyboard shortcuts remain the same, except of course that they then use the new keys. For instance, my "Ctrl+C" is QWERTY's Ctrl+V. You get used to it. It don't think it's an issue. I also don't know of a community behind QFMLWY, but I'm not sure you really need one.