Do I need to wash my sleeping bag after every use?

No.
The less often you have to wash your sleeping bag, the longer the insulating properties will be maintained.

Inlet
A cotton or silk liner will delay washing the entire sleeping bag, as it protects the inside of the bag from dirt, is easy to care for and can be washed quickly when you’re out and about. The thermal insulation of the sleeping bag is also slightly increased as a result of this.

Smaller, superficial dirt can be removed easily with a damp cloth. The entire sleeping bag should be cleaned after 40 to 50 night’s use (less often if using a liner). This is best done by hand or with your own, domestic washing machine.

Please refer to the care instructions before washing and drying.