I like very much when a person who run a milonga invites a different DJ each milonga. But is not good idea keep over an over same DJ playing same music every milonga. A DJ told me one time that he will not play D'Angelis because he didn't like his music!!! I couldn't believe it ! I didn't go anymore there!!
There are different schools of thought.
One school says that if it works, don't break it - in other words, if the crowd likes and expects a certain like of music, then don't change and keep the DJ.
Another school says change the DJ - give the crowd a bit of change and flavor.
I prefer the change,