I have heard the same from friends who have been in a similar position. Their W's have come back after they see that you have moved on somewhat, and the fear of possibly losing you becomes real.
Also, the PMA and building of confidence with GALing and possibly dating, makes you more of an attractive option. A similar option when they fell in love with you all those years ago, whilst you were still confident and single.
As long as you are certain with where your priorities are in regards to saving your M, salvaging a R or calling it a day.
AndyV M38 W36 D7 M 13 years Together 17 years W wants D mid Dec 06 (ring off) W wants separation early Jan 07 (she backdated to Oct 06) EA revealed end March 07 (Nov 06 W first meeting with OM) Hallmark moment "I care for you but am no longer in love with you."