How could they spy on you if it's air gapped? You're supposed to never connect the internet.

I did read  that some researchers demonstrated that they were able to pick up the sounds from a hard disk seeking, and thus reconstruct data from the disk, even if the computer was not connected to the internet. However, that does seem a bit impractical, even for the most dedicated hacker..

Having read the replies, my thinking is that it might be good to use tails for any significant transactions.

As these would be infrequent, one could recreate the wallet each time from the memorised seed phrase, and an online watching wallet.