The primary reason for attic ventilation is to remove moisture from the attic - mostly during the heating season so you do not have warm moist air in contact with a cold roof deck. If your house is 70 years old and there are no signs of moisture problems on your roof decking, then I would say your gable vents and ridge vents are doing the trick and not to lose any sleep over soffit vents.
How importaint are attic soffit vents?
How importaint are attic soffit vents?Asked by dan gregory
My 70 year old wood frame home does not have soffit vents because the bottom of the roof ends at the top of the exterior walls. My spouting butts up against the house. I have a ridge vent and a gable vent at each end of the unheated attic. Should I be investing to get soffit vents intalled somehow?