The correct question here isn't how long, buy why would you want all craft skills at 100. Specially if you just want to do a little bit of everything.
All craft skills are not created equal:
- Fire Building --> any old fire will do.
- Masonry --> walls made with junk bricks will still keep the big bad coyote out.
- Basketry --> you want to make your own bins and high quality plant/food/meat baskets help keep stuff a little longer, but those are easy to trade for.
- Tailoring --> cloth "armor" is almost as bad as grass armor. You will want good thread/string/twine for tools, leather armor and some tools, but again you can trade for that.
- Woodcraft --> good for Pioneer's tools (leathercrafting) and most weapons.
- Bonecraft --> if you are crafting for yourself, you don't really need both bonecraft and leathercraft.
- Leathercraft --> great for everyday wear and needed for some tool and bonecraft schemes.
- Toolcraft --> any loner will need toolcraft at a reasonable level to make grind tools. If your toolcraft is not maxed, you can trade for the tools to make your master armor/weapons.
- Weaponcrafting --> most weapons use wood handles, but you could concentrate on those that use only scavenged parts or trade for wooden handles if your woodcraft is not great.
If you want to make and use your own supreme tools/weapons/armor, you can with those three trade skills in the high 90's and some trading and hunting buddies. For no trading, it will take longer as you will need tailoring and perhaps woodworking and a lot of combat training (Shadow Bears won't share their bones/hides).
If you are a min-maxer who has to have the absolute best of everything and refuse to trade, yes you will need a stable of characters, more for stats than skills.