Uhm?
Just to be exact - are you referring to the giveaway itself or the validity of the keys?
Once activated its lifetime licensed. You can keep backup of your Key.sk file wich is your license for current pc configuration.
In fact, isn't Skype itself already an encrypted but proprietary system? So what's the point in switching to another proprietary provider which you have to trust?)
The structure and encryption of the Skype network allows 'man in the middle attack'
to be made and be possible only if it's done by the owners of the Skype network
or someone authorized by them.
If you accidently forget Skype signed in on
some of your home or work computers and you are chatting by other pc, so everyone who
has access to your computer could just look at your chat sessions, while you chat
to someone else.
Securechat even helps against hackers, who would steal your Skype password and they could do
the same all the time, without you even suspecting this could be happening.