I have a bit of a variation on the same thing.

1) I charge 1 pack at a time.
2) I do not use distilled water. The evaporating and recollected water is, by nature, distilled.
3) Here's the process...
- a) Place your charging container setup, without the pack or water on a kitchen scale
- b) Push the 'Tare' button to zero the display
- c) Place the deflated pack on the platform
- d) Trickle water into the bottom of the container until the scale display equals the advertised pack weight (i.e. 60 grams for a 60g pack)
- e) Seal the container and ignore it until the water in the bottom is gone

The idea is to put the pack back to how it came from the factory without overcharging it. This way you can ignore it until you need it again without fear of overcharge. I'm not sure how this would work charging packs in mass as I haven't tried that. It might be worth some experimentation to find out but I just don't have that big a setup to have to worry about it.