My buddy at Microsoft tells me that in terms of automation, they use the dogma that if you need to do it once or twice, you just do it by hand. If you need to do it more than that, you automate it.
A good rule of thumb. A more nuanced look proves even more helpful: There are graduations between manual and automatic. Semi-automation can be enormously productive, too. (And if you go beyond just automation, there's making your scripts bullet-proof under all circumstances. Which is useful, if you are doing tasks not only a few hundred times but even more often.)