My kids will not quit, they will continue to ask for things until you relent and just do it.
For instance; I could be elbows up in the dishes, covered in soapy bubbles and filth, and they could want more berries. I say something like “In a minute, let me just finish the dishes.” Looking up with their unsettling blue eyes they say in unison, “More” while holding their bowls up.
I look over and shudder slightly, “in a minute, let me finish this.”
“More!” Their eyes a little more unbalanced.
“No! Ask again and you get nothing!”
“MORE!” not unlike the villain from Inspector Gadget.
This time I’m completely pulsed (as apposed to impulsed) A deep shudder fills my being.
“OK! Fine I’ll get you more berries!”
In the end the only thing to do is relent. Remember lose the battle win the war, not sure if that’s what I’m actually doing.