if you're still alive,breathing and competent,you should be allowed to fly.Its just like any other job really,i mean you could just as well make doctors retire at 55 or whatever on the same grounds that those who want pilots to retire use to justify it. after all,if you are for example a doctor, you are required to execise the same standard of care and you need your physical faculties,yet the age limits for them are apparently migh higher.so there should be no set age limit.