It would also be helpful to see all emails connected to the constituent, not just the emails associated with the current primary email. When someone updates their email, the entire history disappears.

Yes, please. The data is used beyond 13 months. For instance, (1) preserving the hard bounce notice in case nobody was monitoring those at the time, so we have some context for why there is no email history for somebody who appears to have a valid email-- this is particularly important if there are multiple email addresses on a record since the bounce comment includes the email address that it happened on; (2) preserving history of a series of soft bounces that help give context to when and why a constituent may have been marked inactive even if there are no other audit trails available, (3) a constituent who engaged with every email before a certain time period but suddenly dropped off may help indicate whether we should search for an obituary, investigate if they left there company (but the company never retires email addresses), or otherwise try to re-engage another way. (4) I was also able to discover, for several email addresses, where the same email address was duplicated across several constituents (due to event guest registrations from 4 years ago) and I ONLY discovered that by being perplexed about unexplained gaps in 2-3 years worth of email history on a record. Cutting us down to only 13-15 months of history is severely limiting data hygiene projects that are only effective if we have the full picture.

13 months does not tell the whole story, particularly when you we aren't able to gather and process bounces easily. We need the full history of emails available.