A pause is normal, only once, when entering the scenery loading range, which is exactly 11 NM. A 18 seconds pause is not normal, unless your PC is extremely overloaded and/or your settings are unreasonably high and/or your remaining memory is all taken by other memory-hungry addons.
Having the scenery loading under our control, thus having a loading pause, is a way to save memory, because this way you are guaranteed that no memory for our scenery is used when your are far from it, while normally FSX is known to allocate memory for sceneries that are far away.