Very true and good pointThe reason that you had a tough time getting the LED off and back on is because it is connected to the heat sink. The heat from the solder was being dissipated through the heat sink, rather than must melting the solder. Lol... It's a catch 22. This is also a problem with more advanced multilayer PCB's. We are past the point of the 1970's bread board, I am afraid...
Corey