The other day I noticed I had over 135k emails within my Archive box in Gmail, I logged in to Gmail and noticed that I was using 11.73GB out of my 19GB free space (This does encompass Google Drive as well, but I rarely use that so that was not where the bulk was from).
I logged in and started removing old emails, starting with the ones with attachments. I found emails dating back to 2007, which I have not viewed since then. I thought about keeping them for historical purposes, but again I can’t think of the last time I searched for an old email. In the end, I was able to bring my allocated space down to 4.11GB, which will help me from upgrading my account for some time.