resetting ECU??

In some of the manuals for my '90GT they mention needing to drive the car at a steady highway speed for about 10-15 miles after doing any modifications to the engine, fuel, iginition or air systems of the motor. Is this really necessary for the computer to adjust to the new mods? I always unhook the negative battery terminal when doing mods. I try to take it for a drive with some highway driving sometime shortly after a significant modification. The reason I'm asking is because occasionally I'll do a little tweaking on something (timing, fuel pressure, spark plug gaps, etc.) just before I go to the track. Sometimes I don't get the chance to take it for a drive before flying down the 1/4 mile...due to weather, lack of time...or whatever. Do you think it makes a difference?