There are two types of SSV rotation--regular rotation and emergency rotation. Both are designed to meet the security needs of assets. Regular rotation is to ensure the dynamity of SSV, and at the same time, to allow the reward to cover the SSV in the candidate pool as fairly as possible. Whereas the emergency rotation usually occurs when the number of signers is close to the limit. Let’s say each round, N out of M signers are needed, but the actual number of signers S is close to or equal to (M-N), the system will urgently replace incumbent SSVs that do not provide signatures. Through this, the activity of the number of signers is guaranteed. Whether it is a regular rotation or an emergency rotation, both will need new SSVs, and the ex-SSVs will take a rest, waiting for the next round of elections. SSVs that are resting will not be able to get any rewards. Due to the requirement of flexibility, SSV's election cycle takes 1 Era as one round.