Latest time a masscheck must be submitted?

Hi

in describtion for masscheck is stated

> If your upload looks good, then you're probably ready to automate
nightly checks. Configure automasscheck to run as a cron job as your
non-root user at or after 9AM UTC. (After weekly-versions.txt /
nightly-versions.txt gets updated in rsync.spamassassin.org::corpus .
If you run it earlier it will break things. )

so "at or after 9AM UTC". But how "big" is the "after"? By when is the
latest time of the day the masscheck submission must occur?

Background: I need to move my server rack where the masscheck box runs
into my office. As this is a quite loud box I would like to make my
submission outside office-hours. The box is triggered via a "plug the
power" via network. Usually it takes up to 2-3 hours for the masscheck
to deal with my corpus. So the question would be: is a masscheck in 
the evening, I'd say after 4PM UTC still possible? And is there an
exact closing time for masschecks of the day?

Have a good one

tobi