Google could care less about your url length. There are other reasons to keep them short. The shorter your url is the better chance you have of somebody linking to you. Also if you have a long URL people tend to run it through a website that generates a shorter url to paste in forums and chat. In the old days search engines had a problem with long urls with lots of ? and & but they have no problem with that any more. Some of the smaller engines might have issues with it.

According to MS support [support.microsoft.com]:

Microsoft Internet Explorer has a maximum uniform resource locator (URL) length of 2,083 characters. Internet Explorer also has a maximum path length of 2,048 characters. This limit applies to both POST request and GET request URLs.

If you can get someone to link to you with a URL that long, I'll be impressed!

Otherwise, my only advise is to keep it as concise as possible