There needs to be a new unit that describes "a speed equal to the fastest humans have been able to travel in space" instead of "light years". Let's call it an "Apollo", since that record is held by the Apollo missions to the moon at 11,080 m/s. Speed of light is 299,792,458 m/s. So humans can travel at ~0.0000367 x light speed, or 349,418,880,000 m/year.

So instead of saying 40 light years, we'd say 27,076 Apollo years.