Vinny,
I'm not sure if you know or not but I'm using a Nature 2 cartridge with my current fill. I left my tub unattended for 6 days. Before I left, I brought the fill to a 10-11 ppm FC(reading was 20 mins after dosing). I also turned it down to 90 degrees. When I got back home after the 6 days, I still had almost a .5 FC and the water was crystal clear. My pH was/is at 7.7 as well. I don't think I would have recieved similar results without the cartridge.
During my first fill(w/o N2), I brought my water to a 10+ ppm and it was gone in four days with just 2 soaks. pH was at 7.4 at that time.
I'll say it again- I'm a Nature 2 beleiver.