Your way is fine if you don't need A/C, heat or a microwave to cook. Also works if you like to take "spit" baths. I see what you're saying and it may work for your type of camping, but you're really limiting power and water. I do what you do on an overnight stop, but not for 3-4 days.
I can hook up my power, sewer and water in less than 3-4 minutes (power reel, power hose and SaniCon). I can also dump my tanks from inside the coach. When I'm ready to leave, just a couple of minutes to put water, sewer and power cord away.
