Earlier quoted context omitted.
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?
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.