Depends on how you use your titles. Just use it like you think it suits best for the visitors. Most of the times it will be the same for the search engines. But just try both and analyse what brings you what you want.
are you talking about domain name length, or webpage title length? For webpage titles, make sure your title, meta keywords, meta description, and page content all match, ie...have related words in them. try to use permalinks when possible to make your titles very descriptive.
It doesn't matter with length. What's important is to keep it attuned to the content with target keywords in mind.
well if you look at my site in my sig the very last one you can see the website title is very long... is that ok?
Page titles can be as long as bout 60 to 80 characters in length, with 2-3 of your primary keyword phrases worked in -- avoid keyword stuffing and instead work the phrases into a very brief statement.