I did the same thing. I hated having to upgrade perl or java. A 4 hour job always took 7 or 8 hours. No matter how well prepared everything was, invariably some off the wall dependency would need a last minute update in the middle of the compiler process...Back
when I was application/network manager for a firm in NY, I'd schedule outage and add an hour or two based on complexity of job.
But if there were other application dependencies who need to time their processes, even when the job is done, I'd wait until the announced up time.
It got to the point that I told our staff to tell everyone the server downtime was going to be 24 hours minimu just to deal with all the unexpected aftermath without having to deal with customers' withdrawal symptoms over their e-mails.