So, after updating, device memory will be cleared and I need to reactivate device with seed? Right?
Can't it be updated without clearing memory?
The latest update worked this way for me.
Trezor T - updated with no issues
Trezor One (two units) - both units the upate completely wiped memory and warned me first that I had to have my recovery words or move coins to another wallet first. I recovered both units after the update with their 24 words seeds.
You don't have your seed words backed up? There should be an offline, hand written copy put somewhere in a safe place. If you use a device like a Trezor or Ledger there is always a chance it can go bad. If you do not have your seed words all your coins would be lost. Not a very good practice.
Writing in a paper and having also a notepad stored on 2-3 usb copies.