Reading MediaGuardian I was struck by the following journalistic advice by Oliver Burkeman: "Be prolific rather than perfectionistic - do the very best you can but don't stress about getting every word exactly right".
Unfortunately I remember one particular article where the journalist (who I won't name) libelled the Homicide: Life on the Streets (soon to be shown on ITV4) producers and thought the Aaron Sorkin dramady Sports Night (now showing on ABC1) "was the equivalent to Match of the Day". Although to be fair that's not unusual on the Guardian/ Observer in terms of inaccurate media/ entertainment stories .
However I still think it's good advice. The more we write, the better we get - although obviously developing self-critique techniques can help us learn and improve. Strangely I also agree with not stressing about getting everything exactly right, but the problem with those aforementioned errors was that they were easily fact-checked via Google in mere minutes.
I do think research is important as long as it isn't obsessive or ends up becoming an excuse to actually avoid getting on with the writing. However it's important that any fact a reader is likely to know is accurate. So while they might not know red giants turn into white dwarfs when they die suggesting that the moon is made of cheese might irritate and detract from the good things in your script. That's why I spend the extra couple of minutes googling the facts in my scripts.