From EULA :
"9.2 Inactive Skype Credit.
If you do not use your Skype Credit for a period of 180 days, (including Skype Credit that has been allocated to you by a Skype Manager administrator) Skype will place your Skype Credit on inactive status. You can reactivate the Skype Credit by following the reactivation link in My Account at https://secure.skype.com/account/credit-reactivate
From FAQ :
On ne regarde pas l'avenir dans un rétroviseur !
IMac Intel Core i3 3.2 GHz - RAM 12 GB - OS 10.7.5
Skype 18.104.22.1686 + 22.214.171.1243
Logitech usb headset or Jabra 250 bt