I have made a test on my side, when "Start an approval" reaches its timeout, the approval would always stays in the “Received requests”, and wouldn’t dissapears from the user pending approvals.
You could create a flow as steps below:
Add a proper trigger, here I use "Manually trigger a flow" trigger.
Add a "Start an approval" action, click "Menu" button, then select Settings option.
Within Settings for 'Start an approval' panel, within Duration property of Timeout area, type the following formula:
Note: The PT60S is ISO 8601 format, it indicate the timeout of the "Start an approval" action is one minute. If you want the timeout of this action to be 24 hours, please type the following formula within Duration property:
When the "Start an approval" reaches its timeout, the flow would run as below:
And the approval would always stays in the “Received requests”.