Blueskybird - concessions at BA are pretty good, remember that taxes are different from various airports though which can make a big difference to prices! You get standby tickets so depends how your nerves are if you want to make much use of them - you have to be prepared to run to the gate and sometimes will only get on by having a crew seat.
After 7 years you get a free ticket and then i think its after 10 you get a better ticket - I will leave that to someone who understands it more to explain as its my partner who has those concessions,ive got a while to go yet!
An example of a fare - a couple of years ago we got tickets to Mauritius for around £100, Bangkok was around £120 for two of us.
Also it works on seniority as to who gets on the flights.
hope that made some sort of sense!