I’ve also had some bad experiences with rates being raised on domains. That still ends up feeling like a risk to me, as the problem of domain squatters has not been solved, and the “solution” being employed seems to be continued rate hikes and exorbitant pricing for “premium” domains. It makes buying a domain for email not seem worth it… or at least not without its own long-term risks.
My current project has been trying to reduce my footprint, by deleting old and unused accounts, so any future migrations will be easier. I’ve found with many sites, this is easier said than done. For example, I deleted my Venmo account at least 2 months ago, yet I just got an email from them yesterday about reviewing privacy settings. Did they delete my account? They sure didn’t delete all my data if I continue to get emails. I’m betting they just set a ‘delete’ flag in the database. The lack of accountability and transparency on these things is really bad.
I've actually split the accounts. I have a Gmail which I use for "throwaway" accounts, like shopping sites where I don't care if I lose access. But it's probably better to exercise some account hygiene and do some spring cleaning every now and then.
There are a million services that assume that if you have access to the email content you are the account holder. Google claims they don't recycle email addresses, but if you lose your domain, the next owner has access to all emails from that point forward.
If something happens and you're unable to renew your domain, are your next of kin out of luck?
I'd say "don't do that". I had a friend pass which I knew had a custom domain for email, I told the relatives they had to be on the ball regarding renewal.
At least my registrar will keep sending invoices for a few months without letting go cough cough, so should be enough time to get the certificate of probate. With that the heirs should be able to get the invoice so they can pay.