Skill rust doesn’t really make much sense as it is implemented. I play with the option that makes it so that you cannot rust points away but you can lose the benefit of practice, making it take longer to level skills. Because that’s more or less the closest to reality.
The key thing to know about how skill retention works in real life is that although there is a refractory period of sorts after long periods not using a skill, where the skill will not be as strong as it was, the skill doesn’t quite go away. The neural pathways which governed the use of that skill have not gone away - they remain there. What happens (in real life) is that the neurons become less and less responsive as they fall into disuse. However as you use those neural pathways, the neurons become more sensitive again, and the skill is quickly restrengthened.
As an example, if you take a professional sports shooter, take his gun away for ten years and then put him on the range, he will a) still be a better shot than most people, and b) rapidly recover his skill. So what should skill rust be like in the game? Currently it is treated like a weird kind of progressive skill-based amnesia.
It should be a fairly temporary debuff. Like a negative to a stat. ‘Practice’ can rust away, that makes some abstracted sense to me. But the rusting of actual skill points away should be handled very differently. First of all, you should not lose the ‘knowledge’ or recipes that you’ve gained. Just because you’ve rusted below the threshold for a recipe doesn’t mean you shouldn’t be able to craft it. It might, however, take longer. Secondly, recovering from skill rust should be far, far faster than having to relearn the skill from scratch. Easily close to 1/3 the time required to learn that skill level the first time around. Thirdly, there should be a limit to how much a skill can rust. -2 or -3 to the skill at most. You simply don’t go from being an expert in something to being completely inept. Not without brain trauma of some kind. Until someone’s character survives long enough to worry about Alzheimer’s disease, let’s keep things in perspective.
In other words, your skills don’t actually degrade so much as a modifier is placed on them with disuse. This would affect how effective that skill is (someone with Firearms 4 and -2 rust would be effectively firing with a 2 Firearms skill) but not your capabilities (someone with cooking 2 and -2 rust would still be able to make coffee but it would take longer and be more prone to failure).
