Cumming is an explosive event. Several things happen at the same time. The feeling of orgasm goes through, the prostate releases sperm and the willy starts to squirt. After 15 seconds it is over and the interest for more disappears.
In young willies they are hardly distinguishable because everything goes so intense and fast.
However, the different parts of cumming can be separated. For example, it is possible to feel an orgasm without shooting. But also to release sperm without orgasm.