The cost of the down sleeping bag is quite expensive; obviously, you have to take care of the bag. If you care the bag properly, then it will last long for years and would provide you warmth and comfort on your backpacking trips.
While you are ready to clean your sleeping bag, ensure that you are following the manufacturer’s instructions to avoid damage. Do washing only when the bag really needs it. Keep in mind that each time you wash the bag, it would lose at least a bit of its loft. The dry cleaners usually use the solvents to wash the sleeping bag, so avoid using those. Avoid using agitator or top-loader machine as they may harm the baffle construction.
Using hand wash in the tub and using front load washing machine would be the right choice. While using the washing machine, maintain the gentle cycle, and use cold water. Using mild soaps will be best, and avoid using fabric softeners. For drying, keep tumble-dry with least heat setting.
Some manufacturers give the warning against home drying machines. However, if there are no hot or sharp parts inside your machine that might harm the fabric, then you will be fine.
While coming to the storing issue, avoid storing the sleeping bag in its stuff sack. If the sleeping bag remains in it, the bag would lose its loft. Hang the sleeping bag flat in a closet and use larger bag.
Do not forget to air out your bag, after each your backpacking trip. In addition, try to turn the down sleeping bag inside to let the air out during the sun. If you keep the sleeping bag clean, then there would be no need to wash it often. If you wash the down sleeping bag after your trip, means you are ready for your next trip.