Norse wrote:He was mentally ill too, though, to the point where he was deemed unfit to handle his own affairs. All in all I think it's unlikely that a person like him would be able to maintain any sort of groomed appearance if he was on his own, regardless of what look he preferred.
All speculation, of course. But I'd theorize that if he appeared fairly groomed around 1970 he was a) not that ill at the time, i.e. he had a job and a place to live or b) institutionalized.
Given what we know of his history both prior to and after 1970, I'd further suggest that b) is the more likely alternative.
Also, the fact he walked into an apartment that was no longer his. Which might either mean he left his current place to go to his former place, or he was released and had no current place to go, so he went to the only apartment he was familiar with.
Or... maybe he was just out of butter...
Since this was in 1970, after the final Z murder, all that would be required, health-wise, would be for him to become periodically lucid enough to write letters. And other than the map, the complicated ones (ciphers) had already been sent. The complexity of the Z letters seems to have been going downhill starting around this time, much as Ross' mental abilities.