Hearthlings are constantly on the move - running, fighting, exploring, etc.. They rarely get a moment’s rest. In real world, this would result in a real, lingering smell of sweat and the stiff, worn‑out feel of clothes that have been worn for days on end. This reality suggests a new mechanic: Dirtiness.
The idea is that energy lost on activities should gradually increase the dirtiness of the gear we’re wearing. While dirtiness increases, the gears bonuses would start to diminish - perhaps increasing percentage of stat boosts lost.
Washing would be next great use of bar of soap: in a barrel, or newly added washing tub, equipped with a bar of soap, a Hearthling can cleanse their gear, restoring it to 0 % Dirtiness and regaining all its original bonuses.
Also, dirtiness could make it easier for agressive animals to spot us, as the stench would irritate their noses and make it more probable that nearby moose would attack us, because of all the sweat our birchbark clothes gained while we were chasing critters.