Okay, I have listened to lots of music in my life span, and it seems that when I hear very well produced and arranged mixes, seems like the synth melodies are very fluid. What I mean is that the synth melody usually last 8 bars, however sometimes 16 bars......and their are multiple synths playing within in that 16 bar to help annunciate certain parts of the melody...

when using google to help coach me on melody making seems like its only 2 bar at the most......... Or that is just what maker only want to show?

here is a good example of longer melodies that I am into...
Viken Arman live @ Belvedere des Caillettes for Cercle - YouTube