I would imagine, assuming one can handle take-off, and re-entry then any age would be fine for space flight, to which, I imagine will get easier in the future.

At the moment, rough and tumble rockets to blast off, but logically I would think that as these technologies improve, not only will safety standards improve, but also issues of stability making it easier for the elderly to get into orbit.

I imagine this certainly will be so given that rockets present a much faster method of transportation around the planet, will be quite interesting to see how it all develops.