This question might be way too opponent-dependent but what the hell, I'll ask it anyway. If a solid regular raises from late position and you call in the blinds, how often are you check-raising a KXX or AXX flop with air? If it's just a random regular whom I don't have a ton of history with, I do it maybe 10% of the time. Too often / not often enough?

PokerStars No-Limit Hold'em, $2 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

UTG ($220.70)
MP ($468.65)
Button ($230)
Hero ($201)
BB ($197.35)

Preflop: Hero is SB with 4, 4.
1 fold, MP raises to $8, 1 fold, Hero calls $7, 1 fold.

Flop: ($18) A, 8, 3 (2 players)
Hero checks, MP bets $12, Hero raises to $36