I am thinking of adding additional fiberglass insulation in the attic. The attic is completely unfinished with no floor, so the joists are exposed. Currently there is R-30 of fiberglass. I was thinking of adding R-38 to bring the total up to R-68. I live in upstate New York and heat with hot air propane. Am I investing wisely?

Yes you are making a wise choice since the price of propane is rising by morethan 10% this fall. Run your new insulation perpendicular to the rafters with no space between the batts. Stop about 1" before you touch the roof rafters, don't want to plug up the air circulation in the eaves.