This alone is an important reason to use your own domain. You can forever be in control of your own email address meaning you can have the address for life.
Unless you get divorced.
I've stood in a C-level meeting, and apologized that a critical name brand server failed. Their on-site tech showed up in 2 hours, and told us that the part would take 2 days to get. "BUT THE CONTRACT SAYS 4 HOUR RESPONSE!" Ya.. 4 hours for them to come back with something. Not 4 hours to resolve the problem completely. 4 hours frequently turns into days, or worse on holidays.
Apparently the purchaser didn't understand your support contract then, because the support tech easily made the commitment. How is that the vendor's fault? It's not... it's the fault of the support purchaser for not understanding what they bought. Higher level contracts (with call-to-repair guarantees) are available; if something's THAT critical, then you should have a fully functional spare or even better, a high-availability solution in addition to your maintenance contract, which it appears you didn't. So it was apparently not that critical...