It is a good idea to get new letters, not necessarily because of the date, but for 2 different reasons:
1- New letters can explicitly mention the petition you are applying for (i.e. change a few words from the original letters); and
2- For presentation reasons! Many lawyers insist that all letters be originals, with original letterhead paper and original signature, because good presentation counts a lot for the USCIS. Photocopies are not considered good presentation.
Just some thoughts, but in the end its up to you.
Adjustment of Status: EB-2 (NIW) at NSC
Package RD:2/26/07 | FP1: 3/31/07 | FP2: 7/24/08
I-140 AD 6/24/08 no RFE
I-485 AD 9/25/08 no RFE
If you use the word "issue" instead of the word "problem", I am much less likely to respond to you. I am also somewhat less likely to respond if you use the word "back" instead of "ago", or if you use the word "back" immediately after the word "return".