By the way, LAX-BOS being DeltaOne, entitles the flyer to lounge access at all starting and connecting points the day of departure of the LAX-BOS flight, as well as the day of its arrival. Domestic DeltaOne gets this benefit.
Same with ATL-BOG. So with the example @
jfkeze posted over two days, the flyer would be entitled to lounge access at EWR, and at every connecting point thereafter for the entire rest of the trip, because of the two DeltaOne segments.
Finally, with schedule changes, some folks may be able to convert EWR-XXX-LAX into JFK-LAX, but certainly a YMMV.