Hey Nathan, 

Dropping the mtorrs on the recipes will make them take longer but will make them more delicate. If you are on 2.17.x software then the delicate recipes is about as delicate as you would ever need to get (unless you are doing some medicines or chemicals or something).  

The freeze dryer will only heat the shelves as much as it thinks it needs to heat them in order to reach the set pressure. So if you drop the pressure too low, or the vacuum pump cannot pull deep enough, then the heat rack will never turn on. 

At the end of the cycle when the food is done, some foods just dont pull below 400-500 mtorr, while others will pull to 200 all day long. So if you drop your pressure too low on the recipe it will never turn on the heat rack. You can drop the pressure to 500 for most recipes, but you would need to do some testing and see if the specific food can go lower if you wanted to drop the pressure lower than 500. 

You dont really have to lower the temp setting necessarily, unless the food is turning out shriveled or such. Similar to what I said earlier, lowering the pressure has the effect of slowing the temperature ramp on the tray rack. If the tray rack only has to be at 38F to sublimate off enough water reach 500mtorr in pressure, then it is going to stay at 38F. The lower the set pressure the slower that ramp will be because it will not need to heat as fast to reach the lower set pressure. 

Yes, if you go slower on the freeze drying process the pump will last longer. Candy is about the worst it comes for pump life. If you kept all recipes at 500-700 then you would have no problem with pump life. We have actually been thinking about dropping our stock recipes to that rage so that everyone's pumps last longer, then for the people that really need it to be faster for production then they can up their pressures to be faster still. 

Thanks 

Brent