At its most basic, flight planning is only to determine if you have enough fuel. Unless you are stretching range to the limit, like crossing the Atlantic, it really doesn't matter. Who cares what the wind is at 5000'? Or the temperature, or what the track and corrected heading is. If you think you have a headwind, put a little extra fuel in. Flying an EMS or ENG helicopter you pump on a couple of hours of fuel and go out 45 minutes in any direction you want. If the trip is further, put a little more in. After a week on a helicopter in a role, most pilots have it figured out pretty close. Nobody in Canada ever runs out of fuel and nobody ever fills out a flight planning form. You're going to Uncle Bill's cabin and you know its going to take you .8, 1.6 return, add a .2 for weather and another .4 reserve and you need 2.2 hours of fuel. Do it in your head. Navigation is 100% GPS. You don't care what the wind is because you fly whatever heading gives you a ground track to where you are going. You don't need a map because the map with all the details is displayed on the GPS screen. As in an earlier post, fuel is in minutes and you can tell exactly to the minute when you will arrive. With some of the newer FMS systems like on the 139 you can work out return fuel considering winds, but it takes about as long to calculate as it does to do the trip, and in the end just doesn't make any difference. IFR isn't that different either, just a check on weather at destination, alternate. Most guys just penciled in some numbers on the Low Altitude chart, and erased them at the end of the trip.
Different story if you are trying to comply with a CL1 or CL2 and have weight limitations and max payload goals that drive the fuel to a minimum. But that's a whole other kind of flying.
Malabo