What type and brand of chain are you buying? I am on a mission to see how long I can make this chain go:
I'm running this brand and type of chain on a KLR 650. I have right at 16,000 miles on it, and no sign of wear on the sprockets, and the chain performs as it was intended. I have been running a tad on the loose side...not much, but loose enough that I am tempted to take it up a titch...but I leave it alone. It is not dangerous or overly loose. I ride about 60 / 40 on asphalt / dirt roads. Water crossings. Nasty old red clay.
I have been anal about cleaning this chain. I use diesel fuel and a parts brush with a cut out oil jug under the rear sprocket. I wash and rinse until I detect no more gritty substance on the chain. Then a two mile run up the road to heat up the chain, and I apply Automatic Transmission Fluid to the chain for lube. Everything indicates that this chain has a lot of life left in it.
Based on your description of your riding habits, I would focus on the tension aspect of the chain. With all due respect, I don't see the power available to the rear wheel of a DL650 as a given chain eater. The roads can be rough as the neighborhoods in northern Mississippi, but not Dakar tough. The enemy of a chain is dirt, heat, and tension. And misalignment.
I know a guy that has over 30,000 on his DL1000 factory chain, with no indication that there will be issues anytime soon. He does keep his chain cleaner than most peoples teeth.