Well, it actually depends upon the components that we are soldering; In general, it usually takes 10 seconds for those SMD resistors and capacitors to cool. However, for ICs, which mainly replies on the its volume. For example, it takes about 20 seconds for a small IC, but about 40 seconds for a big one.
In short, the longer soldering time, the longer solder cooling time is. In other words, unless you can't feel the obvious temperature by hand before you power on and do the test.
