When the Thialf arena opened in 1967 in Heerenveen, Keulen-Deelstra went there to work on a comeback. She quickly made much progress, but she was told over and over again that she was too old. Not a member of the Dutch speed skating team, she won the Dutch Allround Championships in 1970 at the age of 32, beating Dutch skating team members such as Ans Schut and multiple world champion Stien Kaiser.
In 1967, Keulen-Deelstra returned to competition at the Thialf arena in Heerenveen. Despite facing skepticism due to her age, she made rapid progress and won the Dutch Allround Championships in 1970 at the age of 32, surpassing fellow skaters like Ans Schut and world champion Stien Kaiser.