Each location demands its own adjustments, so keep an eye on the plant and see how it responds. I used to water my plants less often, and the difference now is that they keep more leaves for longer. If you compare the picture above to some of the ones in the database from Florida gardens, you will see it looks sort of stunted. That is typical for Pachypodiums in the Californias where we get zero rain in the summer.
As for age related differences, I would think that younger plants require more frequent water than older ones, all things equal. They do better when the soil doesn't stay dry for too long. I water my baby seedlings twice a week year round for the first couple of years (and after the first year they are all out in the sun). Once they go in the ground, they do well with much less frequent water. Maybe once a week for the first year or so, then much less.
Your situation will be different if the plant is indoors, I'm just trying to share my experience so you can translate it to your windowsill.