Yeah I disagree aswell. The way I see it is;

Its going to take longer to get her off so longer sex in total.
More in control in getter her off so more in control of whatever you like to do next.
What girl says no to something after you've made her cum multiple times?
Ego boost, your a guy that she may very well brag to her friends about later about being shit hot in bed.
You can both relax after in the full glow of sexual satisfaction.

I reckon she'll be more thankfull of the orgasms than the load in the face, but if you want her to be thankfull about that then frame it as "I love to do this, but you wont get it so you cant have it, sorry. maybe if you were a bit free minded I could give you that"

Try it