May I ask, is this a personal preference, or is there a technical reason why this might not be a good idea?

Thank you for your response.

I mis-typed... I *did* write down my 12 word seed phrase.

I will research how to boot Tails from a USB stick. 

(Reader of this board for a year, this is my first post).

Please find holes in my cold storage strategy.

Here's what I did:

- downloaded Electrum 3.3.8
- verified GPG key of the software sig via GPG Suite
- create a copy of the download and moved it to a dedicated USB stick
- installed Electrum on primary computer profile, and then....
- went offline
- created new user on mac (this new user has never been online)
- copied electrum and installed again on this new profile
- created new wallet, wrote down private keys *edit* wrote down seed
- copied the xpub to a text doc on USB
- copied one of the receiving addresses to a text doc on USB
- logged out and went back to the main user, back online

Ok so now my private keys *edit* seed are forever stored offline.  I secured them.  

Now I take the xpub and load up a "watch only" wallet.  

Now I want to test a transaction in and out.  I sent a small amount to one of the the receiving addresses of the cold storage wallet.  Verified on blockexplorer and in Electrum in the "watch only" wallet.

Now I want to test moving a small amount out of this wallet.  I create the transaction, and save it to the USB.  Go offline, logout.  Now login to the other profile, and "sign" the transaction.  Save this to the USB.  Log out.  Now I login to the main profile, load up the signed transaction in Electrum, and the transaction works.  Verified on blockexplorer, verified in the "watch only" wallet in Electrum.  

Last step - go back into the offline profile and fully delete Electrum.  



Aside from what will be the most common issue is I need another computer (use a separate machine, airgapped, never connected ever), what holes are there in my strategy?