You can unstake your eGold at any time.
The entire unstake process takes 10 days:
you first have to initiate the unstake process, through an unstake transaction.
and 10 days later, you will need to finalize the withdrawal of your unstaked eGold.
Only after those 10 days and only after you successfully withdraw your unstaked eGold, they will be available in your wallet.
During those 10 days, your eGold will not be eligibile for any rewards.