Originally Posted by livedarklions

Not the same thing, but I used to do plenty of long rides on my FX 3 (125-168 miles in a day). I don't find the aero aspect of it makes much difference even at 20 mph, it's more noticeable in limiting the top speeds than it is in wearing me out at normal cruising speeds. I also think it makes up for any fatigue factor in fighting aero forces by being a posture that's slightly easier to maintain and, for me, being a better set up to climb hills. My real reasons for switching to drop bars is because it's a little bit easier on the hands and I really enjoy squeezing out that extra 1-2 mph at the top end of the range on the flats.

Aero generally isn't really that effective against headwinds for the simple reason that they usually are at least slightly perpendicular to the direction your heading--i.e., also a bit of a crosswind. We're streamlined for the air hitting us directly in the face, not the one hitting you in the cheek..