You can greatly reduce the drying time of your firewood with a kiln. Wood that would normally take 6 months to a year to dry you can dry to 20% moisture in 3-5 days with a kiln. With a kiln you can be selling dry wood any time of the year just days after cutting it.
No more storing wood for months or a year waiting for it to dry. You can produce your firewood and sell it on demand instead of speculating what the firewood market may be like and how much you will be able to sell 6 months or a year ahead of time.
A kiln can produce cleaner wood. The heat of some kilns will kill the bugs and fungus and prevent mold and mildew that grows on wood while drying in moist climates. This is especially valuable if you are selling bundled firewood in stores or shipping it out of state.
These are some advantages of using a kiln but you also have to weigh the costs of acquiring and operating the kiln with the benefits. There is the cost of energy and the extra handling from loading and unloading the kiln.