What about Ctrl + A, Del? I'm only half-joking. How many emails older than 3 months in a mailbox growing beyond GBs are really worth saving? I don't want to sound harsh - that's just how my mailbox looks like.
You're throwing away all your history in doing so. Personally I never want to delete emails from loved ones, which is where most of the storage ends up going anyway.
I agree that genuine exchanges with the people in your life should be kept. As well as anything about purchases, invoices, salary notes etc. But my point is that these days newsletters, spam, notifications, ads, etc. make up a huge part of many people's email traffic.
If you are in the habit of exchanging a large amount of documents and pictures over email, a dedicated storage solution might be more appropriate.
Work-related communication, as in freelancing, might deserve a separate mailbox that is kept clean of unimportant things.
Is your mail box filled by lovely emails rather than newsletters/ads, really? Text emails could take small amount of volume. Maybe many photos are attached?
Newsletters & ads typically link externally to images rather than embed. I would guesstimate less than 10-20% of my storage (not total number of emails) is newsletters.
You’d be surprised. A few days ago it was useful to look back at emails I’d received over a decade ago to work out when and how well some specialist book I’d books had sold.