When would you seize the FSMO roles on your domain?

Question $2$ options:

When you plan to move the roles to a new server that has been ordered to replace the current server.

When you are creating over a $1000$ user accounts between two domains.

When there is a critical hardware failure and the current FSMO server can't be brought back online. The current FSMO server is not able to boot into the NOS.

When you plan to upgrade your domain to a newer version of Active Directory.