Essentially the current livery was launched on Concorde in 1997, some 18 years ago. It was introduced to the wider fleet a few years later, and has been tweaked on the aircraft a few times since. Given it's just one them the UK superbrand again, I am not sure there's an urge to change somethinfg that remains incredibly effective. Remember BA often rely on brand loyalty to make up for their inability to compete on hard product.