I prefer not to use exit sub, but goto a label at the end of the macro where the macro is tidied up e.g. as follows
Code:
Sub Macro1()
Dim orng As Range
Application.ScreenUpdating = False
' code of macro
GoTo lbl_Exit
' more code
lbl_Exit:
Application.ScreenUpdating = True
Set orng = Nothing
Exit Sub
End Sub
I cannot comment on the CPU use.