Having instructed GA (PPL / CPL) pilots at a busy international airport (in the good old days when they encouraged GA at the same airfield) you become accutely aware of wake turbulence both on takeoff and landing. Its rate of disipation does vary according to external factors (wind strength, direction, ground features) and yes sometimes you would be offered a takeoff earlier than you might expect, but it is always the pilots discretion as to accepting that clearance.
The thread does bring back memories of doing "clover leaf" circuits when the wind was light so as to avoid the turbulence (takeoff 33, touch and go onto 24 back to 05 - keeps a student mentally active !!)