I find myself having another email account is actually helping me to better manage my emails that are beyond saving in my main (15 years old) email account. Now, I can:
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Choosing a new email service that’s better and more interesting than my previous one.
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Slowly changing my email address on various services that I am using daily. If I am not using any service today, I probably won’t use it often or might not use it anymore. So, I left the old email registered on those services as-is.
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Labeling my emails, better organized inbox, archive, etc., which is not manageable any more with 15,000+ unread mails in my main email account

I am very happy with my new email account. Having a new email after 15 years is better than I thought.