When is it appropriate to use "late" when referring to someone who has passed?
Solution 1:
Yes it is most appropriate for use with those who were recently living.
For an explanation:
The sense of "deceased" (as in the late Mrs. Smith) is from late 15c., from an adverbial sense of "recently."
-From http://www.etymonline.com/index.php?term=late&allowed_in_frame=0