That's another thing to consider, but depends on the case: if the domain is left expired, there's 45 days after expiration to renew and another 30 days Redemption Grace Period before it's actually deleted. If the domain is "hijacked" (unauthorized transfer), then the registrar is in violation of ICANN policy[1]. If the registrar decided to shut down for some reason, you can still always move your domain to another registrar.

[1]: https://www.icann.org/en/help/dispute-resolution#unauthorize...