I like the idea of ability bonus giving a time discount on proficiency training, but I'm thinking that 250 days for skill proficiency might be too short. I can see 250 as the base for tool/language proficiency, but I'm thinking that for actual skill proficiency, I'mma bump it up to a full year. I'm also thinking that certain types of tool proficiency shouldn't take that long to master; like most games and maybe land vehicles.
So, what've we got for the default tools that you can get proficiency in? There's all the
artisan's tools
musical instruments
navigator's tools
thieves' tools
there's the kits,
disguise kit
forgery kit
herbalism kit
poisoner's kit
there's all the gaming sets,
and land and water vehicles.
I think most gaming sets I'd set at something short like a month or something, unless it's something crazy like "elven 4-dimensional hyperchess" or something. Really, how long does it take to learn a game? And it's not like it's a major powerboost, being able to play poker. Vehicles I'd probably set at six months, and I'm thinking that pretty much everything else works at a base of 250 days. Might boost that to a year for some of the artisan's tools, like jeweler's tools or alchemist supplies or the herbalism or poisoner's kit. And then let folks with high Int or Wis or Dex, (depending on the tool/kit type) get a 10% time discount per bonus point.