Let's just say your children whine and complain endlessly when you say no. Eventually you find yourself giving in just because they have more energy then you do and somehow keeping the peace seems like a way to preserve your sanity. Here are some options. I hope you'll consider experimenting with them on a day when you are not sleep deprived or on edge.
1. Pick a single response like "I know" or "It might seem that way" or even "What did I say?". Next time they try to engage you in battle "Go brain dead!" - only allow yourself to reply with your phrase. Just keep going about your routine.
2. Try an enforceable statement: "I charge $1 per minute for listening to arguments. (If they don't get an allowance feel free to accept payment in toys, electronics, or work)
3. Use the "Uh Oh Song": lead with empathy ("Uh Oh, arguing with me is not a good decision! ) followed by a consequence ("Time for a little bedroom time")
The next classes on the campus of Zion Lutheran Church in Belleville, IL are in September. Don't forget the great resources at http://www.loveandlogic.com/. I recommend the CD(and don't earn money for doing so) Love and Logic Magic When Kids Drain Your Energy.
I am available by email.