Staying Comfortable on Longer Rides
Simply changing your riding position by gearing up 2-3 gears, and standing out of the saddle as if you were climbing a hill even when the road is flat will help promote blood flow to other parts of your body. Be careful to add extra leg power to the cranks when doing this so your bike doesn't go backwards. Don't know if you've noticed that I do this at least once every ride. Even 10 seconds feels good before you hit the saddle again.
Also switching your hand position on the bars often from riding the tops, to on top of the brake hoods to going into the drops will help with the pressure you can get to your ulnar nerve in the palm of your hand which causes that numb feeling you get especially early in the riding season.