I wouldn't worry about it myself. I am sure that the oil will absorb some moisture over time, but I have never seen this to be a big problem. If the oil looks good and is not overfull because of gas in the crankcase (which you would be able to smell),I wouldn't worry about it. I only change the oil in my 1973 Chevrolet pickup every three or four years since it isn't run that much.
For what it is worth.
Jim
