Ha! I remember Cadfael, I think it starred Derek Jacobi, he of I Claudius fame.
I get that they took their vows in the past but they're still the people that took it in the present day. Take a lawyer, for example, who takes their bar exam in their 20's - they will still be a lawyer in their thirties, forties.....etc. They don't stop being "oblates" after they take their vows because the term refers to the person that took them not the act of taking it so, as long as they are still living, they are still oblates.