Like Henry said, if it ain't broke then don't fix it. Soffit vents are relatively new. Codes generally require 1 sq.ft. of vent per 300 sq.ft. of attic space. Because of that, I can drive through a neighborhood and tell the approximate size of the houses. Newer houses are using soffit vents and then 1 sq.ft. square roof vents about 3' down from the peak and along the back side of the house(Some use ridge and gable vents though). Nothing real exact about it but you get an idea when you see 4, 5, 6, or 7, etc. vents all lined up in a row what the square footage is.
Your subject mentions dam ice but your comments don't mention a dam ice problem. Do you a dam ice problem?