John R81 wrote
But on the up-side, flying the same aircraft means that you do spot when something changes.
Not always if the change is gradual. Before the days of HUMS, I visited a base where one crew flew the same aircraft everyday. They were both very professional and were fussy about the state of the aircraft. I performed a line check on one of the crew and thought that the aircraft was a bit rough compared with the last time I had flown it a month prior. A track and balance showed it was close to the limit and had deteriorated, but the crew which flew it every day hadn't noticed.