I hope this post falls under the right section but if not someone please let me know.
A songs notes don't change unless there is input from someone actually changing them, in clearer terms c3 wil always be c3.
So with this in mind if you write a great emotional melody, that melody should always be emotional and great, disregarding changes of taste and more developed skill.
Now to get to the point of this post. Write in a piano vst; leads, plucks, even pads for future use.
Overtime you can build a collection of midis labelled for different genres or moods, eg "128HappyLead.midi.
This is important because it streamlines the workflow when making music so the process can be quicker and more a flow like state.
Once you get the song arranged and things laid out how you like then if you like you can adjust the midi to better suit the track.
This is something I find invaluable and I hope others gain from it as well.