I seldom reset screenupdating back to True.
You have to know when to do it. Basically, if control gets returned to Excel at the end of the macro, i.e. the code stops running, then there's no need to turn screenupdating back on because Excel will return to default. (i.e. TRUE)
However, you can get screwed quite easily and this is the only example I have of this.
Create a userform, doesn't matter what it's called and use this code to show it:
<pre>
Application.ScreenUpdating = False
Userform1.Show 'Or whatever your form is called</pre>
Start moving the form around and you'll be "painting" it all over the screen. This is not necesarily a problem, so long as you know what userform is yours. (ok it is a problem because it's a bug that we've created). This feature is particularly fun when you use "modeless" userforms and use a form to display another.
Anyway, I hope this helps. (if you're evil, like me, it's also a laugh to alter someone's code to do this, just to see how long it takes them to fix it)