Burned or damaged leaves should be removed immediately. The plant spends energy trying to repair the leaf, to me, also applys to ending of leaf cycle.
I think you're wrong on this. The plants pull nutrients and water out of damaged, or mal-nourished, leaves before they drop them.
Also, plants don't really "heal" from nutrient lockout/burn. With many essential nutrients, if they are missing during tissue generation those tissues are permanently damaged. When the nutrient deficiencies are corrected, the plants will drop those damaged leaves in favor of new, healthy growth.
I subscribe to the philosophy that leaves feed the buds. Also, if my girls start to drop their leaves, I take it as a sign they are deficient in some nutrients (usually nitrogen, or potassium/phosphorous/mag) or they don't have enough light penetrating the lower leaves. This is true through the whole duration of flower. I don't want my girls to drop their leaves, ever!
That being said, I have only one girl that burns easily in late flower (she is already a light feeder) and insists on dropping her leaves. All the other girls I've ever grown have responded nicely to having proper, balanced nutrition throughout the entire grow.