event "close program" Main question:

in my addon, i create a python-thread, for do not blocking UI. (1) its wrong?)

thread created on checkbox-"on", and destroyed on "off".
problem when checkbox is "on". when i close blender, blender does not close :)

i find this solutioin, but not work for me, callback not fired

i need thread for "filewatch", and do something on os "file-modified" event

how can I solve this problem?

sub question

i have a class extends from bpy.types.PropertyGroup and 

checkbox-property = bpy.props.BoolProperty(
    name="Switch",
    description="",
    default=False,
    update=checkbox_update_handler
)


default=false not work in some cases.

how i can set always false, when blender\or new file startup

Thanks!
I found a solution also based on atexit,
but thread need property daemon=True.
Then python interpreter do not wait he will complete the work and fires atexit-callback