I don't think too much hurts anything... but the recommended rate is 1 ml per gallon - if you are going to bag it yourself, you can save a few $$$ and run 60 ml or so... & change it out a little more frequently.
This is what I use to do, then I got to where I didn't want to mess with bagging it, being it's so cheap ($7 for a 100 ml bag) & last so long, I just started using the 100 ml bags.