[Cooker] When to mirror?

[Daniel Tabuenca]

    I've been trying to mirror the new distribution but it seems to be
constantly changing. What is the general rule for when a mirror is ready
for testing? Is there a particular time of day that the mirror is static
so that one can create an  ISO? Usually even after I mirror if I mirror
immediately again I get 3-10 files that have changed. When is it safe to
actually burn an image and try to install?