Some Details

(i) See here. I thought that Time Patrollers would be able to cope with longevity by editing selected memories. However, they are unable to do this with Luis Castelar, the Conquistador who stole a timecycle:

"'He will receive secrecy conditioning. It's harmless in itself, but makes a person unable to reveal anything about time travel...Would you rather we killed him, or wiped his memories and left him mindless?'" (Time Patrol, p. 733)

So it seems that only the linguistic and other such practical memories artificially implanted for Patrol purposes can be subsequently erased?

(ii) If Everard departs New York, January 1990, to spend say three months in a historical period, then he can return to New York in January 1990. He need not leave his apartment empty until April 1990, although at least once he lent it "'...to an operative who needed such a base for a task of her own.'" (The Shield Of Time, p. 180)

However, I expect that Everard would always return to his apartment after he had left it, not before, and also that Wanda would keep her visits to her family in chronological order. But I have found one occasion when she seems to operate differently. She telephones Everard at his apartment from her parent's house about her assignment in Beringia in February 1990 (The Shield Of Time, pp. 176-178). They "'...stayed in touch after Beringia...'" (p. 295) and thus both became involved in the Lorenzo de Conti affair. After that, Everard telephones her at her parents' house in January 1990 (pp. 430-431).

Being at home in January after being at home in February is not a straightforward contradiction because this is a time travel story. However, I think that Patrollers would avoid such discrepancies if possible.