I like the half-life of knowledge a lot, but it should better take into account that using your craft actually improves what you know. This half-life is more a thing for stuff you never use in your life. And is there anything good to remember things that have no use for you? It's just wasting space in your head.
So having your skills expire after a while might actually be a good thing.
So having your skills expire after a while might actually be a good thing.