My mechanic for our low-mileage classic says the oil should be changed at least every six months any time after the car is driven, since some of the additives added by the manufacturer will probably be less effective after six months once they are exposed to engine operating stresses. Modern oils are quite good and it’s not like the oil is going to suddenly change into mush after six months, but you are stacking the odds in your favor, and an oil change is relatively inexpensive.
Unlike modern oil, modern ethanol-based fuel is worse than it used to be and that may be even more of a problem for cars which are not driven very often.