I think two pregnancies during her MLC prolonged it.
Read the long post by Hearts Blessing on here. It was my wife to a T. AmyC also had amazing insights.
Manliness is next to godliness.
There are several fantastic resources which I read during my years of hell. I've not heard of the ones you mentioned but I will look them up. It's so important.
Whenever I've paid attention to this subject in my own marriage we end up having sex more often, as if by magic.
There is literally nothing bad that can come of paying attention to this matter.
Me: 46 W: 46 T: 23 M: 20 DS12 DD11 DS5
W left: 01/28/08 Discovered OM: 02/26/08 W back for 9 days: 04/08 W returned 05/21/08 EA/PA - 01/08-07/09 W's MLC 2008-2014 (realised this much later)