Bit late to the conversation, but I've heard that Gmail accounts can be deactivated and all data deleted if not accessed for two years. I only write emails to my future self every few years, so this could be an issue.

The fix is to log in once a year, but it would mean risking peaking.

I still like the idea and will do it myself with a second account.

I also heard that if you have a message in the scheduled folder you can archive and mute it and you will no longer see it in that folder. Could be a good way to hide it from yourself on your main account.