Long domain names and search phrases

Since I have heard that submitting both primary and parked domains pointing to the same site can cause problems, I would also register a parked domain with a short, simple url, i.e.; www.widgetworld.com, that would not be submited.

Is there a reasonable limit to the number of characters in a url that the main search engines will index? Could I be penalized for submited a URL containing a four word search phrase that's say, 30 characters long? Is four words too long of a phrase for major search engines?
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