How much would you wager on KK preflop?

I think it's more dependent on reads. Although it doesn't happen often, I have gotten reads on people before that they ONLY have Aces or Kings and if that's the case with someone, I probably would be reluctant to complete my small blind with Kings, let alone my stack no matter how deep it might be knowing I'm going for a chop or 4 cards to a flush BEST CASE. On the other hand, some players are so loose and aggressive and bad that I'd probably put any amount all-in with them. By and large though, on average at most stakes, if you can get KK all-in pre-flop, it's a good move because there's only one hand and 6 combinations to make that hand to worry about and you're a huge favorite over the other hundreds of hands and thousands of ways to make those hands.