Why does using a wallet in cold storage make it less secure? According to How to set up a secure offline savings wallet,


  Every time you retrieve bitcoins from your savings wallet, create a fresh savings wallet by repeating the above procedure, and send all your remaining savings balance there.


Why do you need to create a fresh wallet after retrieving a few bitcoins? 

Is the receiving address no longer valid?

How can you create a secure offline wallet, send bitcoins to it, and then test it to make sure that it works by sending a small amount out?
I believe the basis of this recommendation is clients' tendency to create invisible change addresses. A transaction sending the entire balance to a known address eliminates the possibility that a part of the balance could be lost when a private key for a change address is not retained.