I'm guessing at option 1, as you suggest you replace your chains based on wear, rather than on time the chain has been on the bike.
But, there are too many unknown variables. E.g. what is your annual mileage, and is it consistent throughout the winter/summer months?
The bit I'm struggling with is that you seem to be saying that you've got through 6 chains in 10 months, so that means you are replacing your chain every 1.7 months?
I have 3x bikes that I do the most of my annual mileage on and, although I don't keep a record of anything, replace the chain on each bike probably only once per year, so that averages a new chain every 4.0 months. At a guess, I would say my annual mileage is around 5K miles.
I do have one of those chain wear measuring thingys, and replace the chain when it reaches 1% wear. But, my winter bike does reach this point sooner than my summer bike based on doing the same mileage.