What is the best URL length?
In order to have a good lenght for your URL, it is good not to have more than 3-5 words in your URL. According to Google’s Matt Cutts, if your URL have more than 5 words “[Google] algorithms will typically weight those words less and not give you as much credit.”
A recent study from Marketing Sherpa, 2008 Search Marketing Benchmark Guide, shows that short URL’s tend to be clicked twice than the the longer ones on Google SERP (for an equal position rank).