It's a trade off. At 75 degrees (relative to a house temp of 65 degrees), it is drying faster than at 65 degrees, much faster. Most fruits and vegetables have a brief resistance to spoilage that permits them to be dehydrated at that temperature. The key is to get the moisture out of them as quick as possible without catalyzing the breakdown process with too much heat. If you can dry the air out more at 65 degrees then it is even better, but I am usually using ambient air, and so a slight temperature differential helps reduce the moisture in the air enough to make a noticable difference. For spoilage to occur, you need three things, food, moisture, and temperature. Unless you are doing your dehydrating below 40 degrees, the difference in temp from 65 to 75 is not as significant as the difference in rate of moisture loss in the food.
As for meats and such, I don't try and dehydrate any meat or other food that contains animal products (especially raw animal products)that isn't cured first. That is bad mojo. Either you cure it, or you get the temp up to 165 degrees internal. If I am going to dehydrate food that cannot be cured and contains animal products, then I do that in the oven at a suitably high temp.
Room temperature is usually okay for most fresh fruits and vegetables for long enough to dehydrate them. The bigger concern is oxidation and/or enzymatic decay, which turns the product brown once it's meat has been exposed (as with a peeled banana or a sliced apple sitting on the counter). To counteract the browning process, I like to use everfresh. Bascially Ascorbic Acid. The application of a little sweetener helps the flavor as well, as some things like Bananas loose some of their sweetness when dehydrated.
I would love to have a freeze dryer, but that is an expensive piece of equipment.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)