If the depositor does not withdraw funds by the end of the term, the agreement may be automatically renewed, provided this is stipulated in its conditions. Renewal typically occurs for the same term, but at the rate applicable by the bank on the renewal date.
This is where the main risk lies: the new rate may be significantly lower than the previous one. A deposit opened during a period of high rates, when automatically renewed during a period of declining rates, will operate under new conditions, and the depositor will only learn of this upon checking the account.
The opposite situation is also possible: with rising rates, renewal under new conditions is beneficial, but only compared to the previous agreement, not to better available market offers.
Practical rule: mark the maturity date and compare your bank's current conditions with market rates shortly before it. Automatic renewal is convenient, but it is not a decision in favor of the depositor — it merely prevents transfer of funds to a demand account with a minimal rate.