Great writers both highbrow (Graham Greene) and lowbrow (Stephen King) recommend a constant production rate of at least 1000 words a day. Writing is a bit like sport, in that (a) it requires fitness obtained through daily practice, and (b) the more you do, the better you get.
My production is currently way down due to moving from America to Australia, but before the move I was doing well over a thousand words a day. It will take a while to get back up to speed, but I'm looking forward to it. Being super-productive is a wonderful feeling.