I've started doing this and have ended up depending on my password manager to track which emails I need for logging in to a service, which is a bit of a hassle although I think it's still worth it for the reasons you outlined. For example, did I use [service]@domain.com or [abbreviated-service]@domain.com, or was it [service.com]@domain.com...?
The only service I have that problem with is Microsoft since it's a merge of like three different accounts (MSN messenger, Skype, and Office365) so I can never remember which is the right one.
Otherwise my rule is to use the central part of the domain name (no www or TLD), or it's easy enough to just search my email archive for messages from whatever service.
This also happens to some extent in real life. Often when I say that my email is "your-company-name@my-custom-domain.tld" it's met with a "well, if you're just going to give me a fake address…". At which point I have to explain 1) catch-all email addresses, and 2) yes, you can own your own entire domain name.
Near enough everything is in my password manager. I use <service>.<month>.<year>.<nonce>@domain so I have to so to speak.
Using keepassxc + its browser and mobile extensions make this easier than typing the address in myself. I was astounded at how bad the ux the paid pw mamagers I've used is
