Well, I think people are in general the average of the people they spend the most times with (a cumulative personality if you will), therefore I think variety is generally a good thing. Conversely, people may have an idea of who and what they want to be, so too much variety will ultimately be contentious or detrimental to the end goal -- if you hang around with a bad crowd, you may (and I use this in its loosest sense) become a bad person.