Hi Malone, to be honest, I'm less concerned about the length of a clue than I am that it should have a smooth surface reading and that every word (within reason) should be key to the answer.
For example, regarding the smooth surface reading, a clue in Saturday's Times read..
28a Pervert at hotel in course towards conflict (7)
The make up of the answer is fine:- WARP - AT - H, but "in course towards conflict" just sounds wrong. Naturally it's only my opinion, but wouldn't "on course towards conflict" have sounded better?
That said, I know from my own disastrous attempt in a recent CLUELESS how difficult it is to write clues so I'm loath to criticize - but that doesn't stop me appreciating a beautifully crafted clue when I see one, long or short :-)