They only need to buy one CWT BASIC .
Example,
I have CWP-BASIC-NL_666 which has expired on may 2010 .
In this case, my perpetual basic suite only has access to version released prior may 2010.
By applying one CWT, my new expiration date will be Jul 2017, a year from now.
You do not need to apply 6 of these, this is cool right?
hope this helps