My experience over the last couple of years with the D7000 is that the 1-2 seconds is normal. I use SanDisk Class 10 cards. Your experience of 5-10 seconds sounds like the camera is having difficulty writing its last entry to the memory card before shutting down.
What exact SDHC cards are you using i.e. manufacturer, model and class? Check to see if they are approved for the D7000 and at least a Class 6 card.
If you can, get some SanDisk Class 6 or 10 cards and see if it makes a difference. That may not be the issue, but at least you can rule out the memory.
"Red is gray and yellow white, but we decide which is right ....and which is an illusion"