If an answer is repetitive or rambles away from the point, then it is definitely too long, and is generally a bad answer.

But then you can have good answers of different lengths to the same question. One may have more detailed explanations and examples; the other may give just a broad idea. Then it is a matter of taste and of what the viewer is looking for. Some people may prefer the longer, more detailed answer; others may prefer the shorter one.

Because all people are not alike variety is best. So that whether you like detailed answers or prefer brief ones you’ll find something to suit your preferences here. So ideally we should have more answers per question. 

Jorge B. [points out in his answer][1] that we have few users and questions. We cannot do much about the number of users. We can post more questions to generate more content, though my imagination has been running low of late. And we can definitely write more answers. Right now we have [1.7 answers][2] per question; [Spanish Language has 2.5][3]. With more answers per question, some shorter, some longer, looking at the issue from different angles, etc., it will be more likely viewers will find an answer they like.


  [1]: http://meta.portuguese.stackexchange.com/questions/229/length-of-answers/232#232
  [2]: http://area51.stackexchange.com/proposals/64172/portuguese-language
  [3]: http://area51.stackexchange.com/proposals/14456/spanish-language