I don’t do Gmail, but I figure any client for any email provider can do this to you:
I’m looking at my G-mail. I have over 10,000 messages there. Why? Because I thought maybe I should save one, and yes, maybe I should save that one too, and pretty soon I was saving everything and now I’ve got 10,000 messages. Theoretically, there might be some important information in there somewhere, and occasionally I have managed to retrieve some useful bit, but is it worth carrying all this baggage around for that one, possibly useful, bit of information that I dredge up every six months or so? If I was having to pay for this storage, no it wouldn’t. But I am willing to carry the mental load of thinking there are useful things stored safely away in this pile of verbiage. So now I am thinking that maybe I should just delete everything and start over.
I threw away around 8000 messages at the end of the year. I still seem to have, um, 41,287 in the archive. Then again, the archive goes back to 1997. And spam is not a consideration in this count: except for items mocked in this space, spam is deleted more or less upon receipt.