This is a tricky balance as when you perform the upgrades the real question is:
How much time do we spend on QA and when do we time such releases...
For the technical... I use this rule of thumb...
Never deploy if other lines of business have large managed releases. Do it in a stable operation window(as stable as possible anyways).
and use change logs to gauge severity, (See below)
AppMeasurement for JavaScript
From an analytical side I know my key metrics lets say you have 50 or 60 I run trended reports for the key one post code change.
To Adobes credit on updates using this methodology I have yet to break things on my side. Typically these code changes optimize javascript code so things run smoother and faster...
GLTU