I've just come across flights from GLA to BKK with Flex fare but if I change the outgoing flights (even to others on the same dates) the return flight status changes from Flex to Saver.
Should a flight always have the same Flex/Saver status or does it depend on the flights you book it in conjunction with?

Is there a quick way to check a range of dates for Flex tickets or is it a case of trawling through every permutation of outbound/return dates?