Speaking to The Daily Telegraph, the Academy Award winner remarked that she was surprised by the public support following her break-up with Robbins.
Sarandon noted that she and the Shawshank Redemption actor always believed that never marrying kept their relationship fresh, but she is now unsure if their approach to their partnership was correct.
She explained: "I've always liked the idea of choosing to be with somebody. I thought that if you didn't get married, you wouldn't take each other for granted as easily. I don't know if after 20-something years that was still true."
While she initially found the split very difficult to get through, Sarandon added that she now has a more positive take on ending her relationship with Robbins.
"You bring people into your life at certain times. Maybe you have a relationship to have children, and you realise that it's fulfilled after that point."