Most schools don't have word count requirements for the letters - it's usually a "use your best judgment."
Having said that, put yourself in the adcom's shoes. If you were an adcom, would you rather read a densely worded treatise that is long winded, or a letter that is concise? Remember that they're reading not just one, but two rec letters (and some schools require three). They're also reading 2,000 or so words worth of essays, in addition to the pages and pages of application forms. They're not spending an entire day drinking in your words (or the words of the recommender).
Have your recommender keep that in mind -- for them to be specific enough to give examples, but not so wordy and detailed that they lose the reader.