I get the sense that I SNEAK a lot. I'm not breaking the "you can only SNEAK if you didn't do so last round" rule, but I'm very willing to bypass corridors if I feel there's too many Threats, that the Weapon & Gear I currently have is better than what's in the corridor, or there aren't any big Threats in the discard pile. Because of that, I think I often end the game with a large number of Threats still in the deck. That's not an issue with the rules or anything that needs fixing or adjusting mind you – just my playstyle.
because of that I'm reluctant to institute a "one SNEAK per game" rule, but I'm still curious to know how that works out for you.