It's a good rule to live by, and like all rules it can be overridden when the circumstances require.

It's good to instill in your team that Friday deployments should be done only in special circumstances, or they become a habit (and people inevitably end up working Saturday). But yes, sometimes it's necessary.

IMO, if you deploy on Friday, you are promising to be available for fixing it on Saturday... which makes it not really a Friday in the sense in which it's meant.

Don't deploy when you won't be around to support it is a better description; but it doesn't roll off the tongue as easily.

So I should just leave a security vulnerability rather than fix it on a Friday, because I won't be available Saturday?

If it has the potential to take down your site? Unless you have someone who can fill in for you, absolutely.

Really, it will come down to a cost/benefit analysis. Are your chances of the site going down due to being hacked over the weekend higher than the chances of a last minute update taking down the site?

The answer is almost always no (much to a sysadmin's chagrin). If the answer is yes (i.e. another heartbleed), then you are probably going to be working through the weekend anyways.

Read to comprehend, not to argue.

Great, now what am I going to do with my life?

This should on the top of every page here.

See if you like this version better:

"Only deploy on Friday if you like working weekends"

Yay pedantry!

I don't think I was being pedantic. The parent poster was very clear, there was nothing there for me to overstate.