Some HTML fields are best limited in regards to the number of characters used. For example the Title tag should be anywhere from 50 - 70 characters long while the Meta Description tag should be around 150 - 160 characters.
The main reason behind this is due to the number of characters a search engine will display if they use either of these two fields within the search results. While Google and other search engines will read anything in excess of these numbers, they'll only display so many of the characters leaving you with a listing that has a trailing ... at the end. Given that what you write here is possibly the first pitch to a potential customer, it should be as high impact as possible.