The unit is engineered around a 5 hour dive capability.
-5.5 lbs sorb at about 1 hr/lb
-368 liters of o2 at 1lpm is 6 hrs, but assume shorter than 3000psi fills on oxygen
-maintain po2 1.0 for 5 hrs on your o2 clock
Configured like this, your o2 pressure gauge becomes a reliable means to gauge overall consumables. No more o2, no more diving.
We have a handful of photo/video pros using them in the shallows - really amazing in this application (no clutter on the chest), and very easy to turn into a mCCR for deeper stuff. RD1s have been dived >80m and no reason they can’t do more than that.