via Radio Times:
The Doctor Who and Sherlock writer says viewers develop a connection with villains when they first meet them and that continually bringing them back can hamper a show’s growth.
“One of the temptations, particularly if it’s a success is to keep repeating your hits, which means you hear it again and again and again,” said Moffat.
“I always say new monsters are better in Doctor Who because you fall in love with monsters when they’re new,” he told Le Village.
It’s an admission that may surprise some viewers, given that Moffat resurrected the Daleks within three episodes of having taken over the show for its 2010 series, but it suggests the Doctor will be facing some new foes in series seven.