It's hard to think of many services that haven't disappeared or gone to shit over the last twenty years. Even if you have a friend in a company that manages thi

It's hard to think of many services that haven't disappeared or gone to shit over the last twenty years. Even if you have a friend in a company that manages this for you and could help you out they might not be around or at that company in twenty years. Speculation: Best and most expensive. You'd probably need to make a contract with a third party to actively manage this for you. Ideally with your own domain to be able to switch providers. There are existing providers that do this type of thing: I have to do something similar with medical records retention and my retirement within a medical corporation in case I get hit by a bus tomorrow, but your timeframe is longer. Cheapest. Practically if it's fairly hands off and reactive to cancellations or service outages you have a backup on another provider through forwarding or IMAP. Middle ground? Business contact with Microsoft or a similar player. I'm not sure it's worth their time.