From other traders that I've spoken to and also from a lot of the panel here, it seems that 3 trades (if that much) a day is plenty for the mini-indices.
JMowery1987 made some really good points about the difficulties of trading them.
They tend to chop (as has been also been mentioned) so that makes them even more of a challenge if your used to trading retracements, etc.
If you have experience and a good broker (?) and a method which works for you, go for it. But if you find yourself entering more than 3 trades a day on any given day, that's a bad sign.
A lot of traders prefer to trade the YM vs. the ES because they can get better spreads and they can be more creative with their methodologies. There are a few threads here on subject.
Best Regards,
Jimmy