More Boredom

You know those long stretches where there's nothing interesting to do?  Yeah, I'm in one of those right now.  I've watched all the good documentaries on Netflix, I'm not interested in moves or TV shows, it's too hot during the day to do anything fun outside... Boring.
So here's a picture of a wet Conker on a log.

One thing I don't quite get is B Vitamins.  Most notably, niacin, B6 and B12.  Why in the crapping crap are there so many of those in meat?  And what is the safe upper limit?  I cannot feed Conker 4 ounces of pork without there being two times as much B's in it than he needs, and for the grain meals, there's about a level amount so he's still getting twice as much as he should. 
However, there almost always isn't enough of some other B's, like thiamin and especially riboflavin.  There's a lot of riboflavin in kidney but there's also a lot of the other B's I don't need more of.

I am wondering if the NRC numbers are wrong, or if it's safe to feed up to three times as needed of some B Vitamins without a problem, all the friggin time.  Some of them are linked to other nutrients, so that comes into play too.  My concern right now is niacin, since it can be toxic in large doses.  Same with B6 but less so than niacin.  And while Conker isn't getting immense amounts of these B's, he's still getting a hella lot more than the minimal amount and I'm not sure if they will affect him over time, or if it's only bigass single-dose numbers I need to worry about.

I really really want that 2006 NRC nutrition book for dogs and cats but I can't afford to buy a $270+ book with money I don't have.