Do we know for how long Vince was flying at 9-10,000 ft asl? If he was not carrying and using a portable O2 supply, then the possible effect of hypoxia on his perceptions and decisions made while under those conditions need to be considered.
What I recall from my training is that oxygen should be used if flying above 10,000' for more than half an hour, with no suggestion that you can't fly around all day at FL95. (Assuming normal health with no respiratory issues.)
So I fly at FL95 when I can ... which so far has been exactly once, on all other occasions this has been impossible due to cloud or controlled airspace.