This is such a personal decision. When my H first left and was angry about everything I had done wrong in the M, one of the things he said was that sex became mechanical for us. In the couple of months after we separated, we were intimate quite often. Later he said that if sex could fix things that our M would be great.
Sometimes it has made me feel closer to him, like we still have a connection...I believe he felt it too (but then got angry later). I have also thought that if he is getting it from me, then he would be less likely to get it elsewhere..I know that is stupid but...it doesn't matter because nothing has happened there for awhile now.
I have wondered if "performance" issues could be part of this as well. Seems like I have read some things about that and I do believe that hormones could play a part in a MLC.