Kobo Aura Firmware Updates Query

Hi

I have a Kobo Aura on 2.10. It works perfectly and I have no wish to have any kind of upgrade in case it causes problems.

I keep wifi off as much as I can but I do turn it on the sync Pocket. At the moment I do sync my new books through the kobo desktop but I don't actually buy much from Kobo so losing that isn't a hardship.

If I use Calibre to sync my new books from kobo (Ie. Download to my pc and add through Calibre) and just turn wifi on to sync Pocket as required can I avoid any forced firmware updates?

Or will a wifi sync of Pocket be enough if a connection for Kobo to send down any updates?

Should I deregister my Kobo device as well? Or is it safe to leave it registered?

My Warrenty is with WHSmith.

Thanks