I switched all of my accounts from my 15 year old gmail address to a custom domain over the course of a few months, during which I monitored both inboxes. I use

I switched all of my accounts from my 15 year old gmail address to a custom domain over the course of a few months, during which I monitored both inboxes. I used my password manager to keep track of which accounts I had updated. After about three months of updating accounts, I set a permanent autoresponder in Gmail telling people that the inbox is no longer monitored and to please contact me via other means (I don't tell them the other means to avoid spammers getting my new email). Then after another three months, I stopped checking gmail completely. Now, over a year later, I don't check gmail except in rare cases where I come across an account I forgot to update, or am waiting for a specific email that doesn't arrive to my new address. The gmail account still gets about 15-20 messages a week, and they're all basically spam and marketing junk.