it's surely irrelevant provided that the aircraft turn up on time for their planned services and deliver customers from A to B as booked. if they don't, there's a debate to be had - but there could be any number of reasons including trying to burn hours before the aircraft's next major check if EMA is a high winter utilisation base (which I don't think it is) or trying to conserve hours to string out the date for the next major check if EMA base is low utilisation. Or there may be a group of older aircraft sharing a flying programme between them at EMA if aircraft parking there is cheaper than elsewhere in the network. Either way, I doubt the typical customer will have any inkling - or even give a stuff if they had - about it?