I don't have any dessert rules or guidelines. I like it that way. Whenever I've tried to set even flexible limits it causes an insta-riot in my brain. If I'm free to eat whenever, whatever, and as much as I want, then I'm ok with whatever I choose. That's really the key to it I guess, to eat with intention and own my choices. I don't get to eat until I'm uncomfortable or remorseful and then beat myself up for it, because duh! My choice! If I did it to myself, all I can do is own the decision and move on, maybe choose differently next time. When it's my choice, I feel empowered regardless. If I tell myself that I'm weak, or they made me, or it was irresistible, I'm taking all my power away and giving it to external forces, which never feels awesome. I quit doing that a long time ago.
So, with a pint of ice cream, sometimes I eat two spoonfuls and sometimes I eat the whole pint. Some days I have four desserts and some days I have none or one. It all tends to balance out if I go with my appetite and preferences. I don't want to be overly full or not hungry for meals. I don't want to eat only sweets, or snack all day, or mindlessly overeat. None of that feels great, so I tend not to do it, but I don't make rules about not doing it. Knowing I could if I want to makes me not care to, if that makes any sense.