I agree that 35F seems low, but I think I may even go lower or 5 higher, for my desired results this is pretty close. I’ve tried for years to get info from harvest right, but they’ve been mostly useless. I started experimenting about 4 years ago, seriously about 3.
I used to do higher, first 60, then 50, 45 was really a good inflection point but on a whim dropped to 35 on a run and I felt it yielded good terpene preservation. In the end, when doing flower, the goals are max terpene preservation and dry with zero risk of mold. The best test of terpene loss (short of lab testing) is what does your ice water smell like when you defrost the system? If your whole room reeks of terps, you have loss. I am sure my time is a bit longer, but again, less terps lost is my goal, power loss (I agree it adds an hour or two but that’s it as I’ve dropped it) isn’t a big deal. If someone is worried about the power to run a FD, they should spend $5,000 to buy the unit, let alone multiple units as I have.
The ultimate goal of a freeze drier is to dry to a given set point. Harvey right has their unit stay below 500 mTorr a certain amount of time with a certain leak rate and that will ensure the moisture is out of the product. If you wanted to manipulate this you could probably ask them if there is a way to adjust it. I haven’t because I am good with a solid rehydration process that also maintains terps.
About drying, I think you think of it wrong (no offense). If you want to know how dry your flower is get a moisture detection probe with probes on it. Research shows that flower burns best between 8-12% internal moisture. I grow primarily for my wife, she gets bad canoeing at 11%+ so I’ve got her around 10% which is ideal for her. You mentioned a certain RH, this is where I think you think of it incorrectly (I could be wrong here), the way I understand it from your writing is the humidity in the jar %, as delivered from your humidipak, this is RH of the environment not the finished product. I had a hard time crossing that bridge myself. Think of it like this, the freeze drier knows it’s dry when the pressure doesn’t raise, the pressure is a function of the outgassing of the water from inside the product (in this way your view is correct because measuring the resulting output amount should be proportional to the internal amount, but once the level internally to the flower is too low and you return to atmospheric pressure the flower retains any it has inside) as such, the goal IMO is dry, dry and cool with no oxygen seems to allow it to store longer from my tests.
In the end, it sounds like you have a great process. It would be fun to find a way to stop the drier when the flower is ready now. I’ve found that a big paper bag and a few hours at room temp gets it workable, add a humidipak if you want but I avoid them because the absorb some terps, which is again flavor loss.
Torr range shelf temps and times.