I like it when my wife doesn't tell me right away.
If your gf/wife unexpectedly does something naughty while you're not around, when would you like her to tell you about it? Right away? The next morning? The next time you two are playing around? Or maybe hang on to it for a few days/weeks/months?
One of my hottest memories ever was when my wife and I did anal for the first time in months. When I got inside her, I asked her if she missed it. She said "yeah!". I asked her "so when was the last time you got fucked up the ass?" and she said "oh, last week"