The fungal leggings degrade over 30,000 charges of combat, and will revert into a mycelium leggings web when fully degraded. Partially degraded leggings can be repaired using fungal flakes - 10 per 1% - which also requires 12 Crafting and some thread, granting a scaled amount of Crafting experience. If they fully degrade, they will need to be re-created from the leggings web.
The leggings can be cleaned at any point to return the mycelium leggings web, and half of the remaining charges in fungal flakes, rounded up - e.g. 80% charged leggings will return 400 flakes. Additionally, alchemy performed on the leggings returns a scaling amount of coins based on the remaining charges.