Interesting - the couple of times we tried, well before the flight, for my wife, the miles still posted. (Before flight because we were ticketed in the highest cabin on the plane, and wifey was accessing the F lounge as my guest rather than the J lounge). Straight and simple booking once, PE upgraded with my miles to J the other time.

Recall reading about the ff numbers being 'sticky' in Amadeus.

Will try at the lounge one day and see.