I see pretty high loss rates on my machine.
One problem is that the Tormach stand isn't sloped towards the drain, so a lot of your coolant pools underneath the mill where it can evaporate easily.
Scott M had a good idea, and used an epoxy to fill in the tray, creating a sloped surface. The only gotcha is that you have to remove the mill from the stand to do this.
If you're about to buy, I would suggest that you do this modification before you ever install the mill onto the stand. I wish I had done so!