Forum Moderators: Robert Charlton & goodroi
I doubled my density on one site (adding - "Site Domain Name" to the end), but it probably didn't help/hurt.
I would never repeat one word more than three times in a title.
Any fiddling with title tags for density or any other reason should be done with extreme caution. It is high-risk editing based on optimization penalties. Google may even update its historical profile on your site branding you an "optimizer." Hiss! :/
p/g