I would say an office is one of the worst places to work to old age. Unless you have looked after yourself outside of work, then you will invariably be relatively unfit compared to an in the field worker in my opinion. As a man who retired at 62, no way would I advocate anyone being required to work past 65. I appreciate that some have their health and will simply enjoy it. Would also say from a mental point of view an office gets very difficult. Young minds are quicker and able to embrace new technology far easier