Having no expectations (though occasional hopes) on mileage is precisely the reason I'm polite, laid back, well-groomed, and just let the LADY dictate the session. I just mention that I'm opting for a NR, and let her take it from there and I can tell you that in the 7 years I've been sampling the MP industry, a lot of wonderful ladies having willingly taken me on creative and erotic journeys with mind-blowing finishes, and some did it without even bending the rules.
Of course being close to their age and in good shape can help your case: I've been outright molested/devoured at times without even asking for it. Not complaining when that happens either... lol
However I never EXPECT anything more than a manual release; that way I'm never disappointed, and the only way things can go is UP.