Curious - you keep switching between Canon and Nikon
Facile comment. Utterly so. Those are the two biggest-selling brands, and have been since, oh, 1974. How did you miss the Kodak,Polaroid, Yashica models? The guy is old enough to be your grandfather, and he happened to buy TOP-selling models each time he was in the market for a new camera, over an over FOUR-DECADE time span!
OMG--a horrible thought just hit me--he might also have alternated between Coke and Pepsi during that time frame as well!! He might have alternated between Charmin and Angel Soft toilet paper too! And, OMG--what if he also alternately bought BUTTER in the 1970s and then MARGARINE in the 1980's when everybody said butter was horrible for one's health--and then went back to butter in the 1990's, after margarine and partially hydrogenated oils were determined to be bad for one's health!
;-)