To reaffirm that, I'm 30 with 25 years to do, having done 7. Assuming the new legislation didn't happen, I would retire at 55 with seniority of around 100. If I go on to 60, which seems increasingly likely, I may make it into the top 40. Either way, I'm likely to be a Captain (either longhaul or shorthaul) for around twenty years (assuming we stay in business). There are a great number of people who are the same age and considerably senior to me or younger with similar seniority. We will all be Captains for a very long time, therefore anyone joining today had better be either a) very young or b) have no aspirations to a BA command.
Sorry, but that's just the way it is. That notwithstanding, if you are prepared to accept the above, the money is pretty good, rosters are set in stone (more or less) and as you get more senior as a First Officer, your lifestyle will improve tremendously (choice of trips/days off) and current T&Cs are good, although the company are doing their level best to erode those (not that it's any different anywhere else). Just don't mention the pension.