I haven't heard anything (yet) from Teamviewer regarding "a yearly" subscription fee?"
After my initial purchase fee, which was not unsubstantial, the ongoing costs are only for major version updates - like version 11 to Version 12 - which cost me AU$249.00.
Incremental updates (like I got today) are free.
I've constantly run into problems where a client has purchased version 9 or 10 for instance, and refused to pay for updates, so I cannot connect to them because their version is out of date.
The only way around it is for them to download the latest free version of 12 but then we have problems with the 5 minute timeout.