I think I’ve read about this on sage-members (it is also quite possible that I’ve blogged about it, but a quick search did not reveal anything):
You’ve got a major upgrade ahead of you, one that might take too long to complete and on top of that, the company (your employer) cannot halt while you are at the task. So do you schedule to start the upgrade on Friday evening, or on Sunday morning?
For years I used to opt for Friday evening. But it seems that I was lucky. For as I read in sage-members, what if the upgrade does not complete and you need support? Do you have (verified) support 24×7 for everything involved in the process, including hardware, software, personnel (if shifts are needed)? Even if you do, have you ever tested them? Are the support people you contact on weekends of the quality you expect or simply note takers so that you get an open ticket and a checklist while an actual solution may arrive on Monday evening? What if a simple fan fails and you need to replace it?
Start on Sunday mornings. As a bonus you get a full day for rest and mental preparation.