This is a simple tip but something that I missed out on for years!
When dehydrating food, sample it through the process. We sliced portabello mushrooms 4 mm thick (about 1/6 of an inch) and dried them for 8 hours.
After two hours I had a taste – they were slightly rubbery, very pliable and not dried enough for storage – but they were fantastic! I am guessing that they had lost 10-20% of their weight. The loss of weight is purely moisture and the remaining flavor was concentrated.
They were so good that I plan to cook like this in the future (aka using the dehydrator almost like a super slow microwave). If you make them in advance, save them in the fridge (they will continue to dry and will mold if left too long) and enjoy!