I think my biggest leak is...

[StellarWind]

Excellent post. We do spend too much time on the same old preflop subjects that barely matter. Any regular on this forum could assemble a top-10 list.

There is a third dimension to the leaks question, in addition to cost and frequency: effort. How much work is it to fix the leak? Example:

Leak 1: I used to coldcall AJo from LP versus an EP PFR. That leak was fixed the same day I realized it was wrong. I'm not sure how exactly serious that leak was, but fixing it was time well-spent because so little effort was required.

Leak 2: When someone raises my river bet, I automatically crying call without thinking. This is a moderately costly mistake that occurs with moderate frequency. Certainly it costs me more than my occasional AJo mistake. The effort for me to fix this is very large. It's been an identified problem for two months and it's still leaking.

That's why I am happy to read occasional threads about novel or little-discussed preflop situations. If I learn one good idea it's worth a few minutes on my time, even if it doesn't come up very often.