O1/EB1A question: reuse old Recommendation letters ?

I am working on reapplying for EB1A. I had applied a while back and it was then denied after RFE. Some of my earlier obtained recommendation letters (from my previous EB1A application) are still very valid but for their date- they are around 1.5 years old. Is it advisable to submit old letters, or get them dated newly ? Please explain in comments if you have faced this situation