When you temper chocolate, you're converting some % of your liquid cocoa butter to solid cocoa butter crystals. Much of it actually remains liquid, even after you've demoulded your chocolate. It may look solid - and much of it is - however there's still a very significant portion of cocoa butter that remains fluid. Over time, some of that liquid cocoa butter will continue to crystallize. It never, ever, fully crystallizes (there will always be some portion of liquid cocoa butter - it will be much more than you think!).
Why is this important? Because how fat melts is important to how flavor releases. As you've already noted, the chocolate you demould today tastes different than that exact same chocolate 30 days from now. Why? It's predominately because of the above mentioned crystallization kinetics. There's a couple of other reasons, to be sure, but that one has the largest impact.
All chocolate (that does not have inclusions in it, or added volatile flavors) - will have stabilized to the point where trained panelists can no longer detect a statistically relevant rate of change after about 28 days, when stored in a controlled, stable environment. Physiochemically, the crystallization kinetics continue to evolve. However, between 28 days and 35 days - there is no statistical difference detected. At some point - very far out - there will again be a difference (related to hardness, as both the volume fraction of crystals is larger as well as the physical form of the crystals begins to change) - but we're talking years out. If you've got an extreme or highly variable environment, everything above changes.
For products that contain a lot of milk, depending on how it's processed, you can run into something called the glass transition (Tg) temperature, impacting lactose. It essentially turns it from a crystal into an amorphous fluid. This again changes how flavor is released (both due to how it dissolves, as well as how much moisture it's able to hold on to - this gets into specific physical chemistry that i won't go into here).
Also be aware that your packaging can impact flavor (either via diffusing aromas from the packaging into the chocolate itself, or by letting the aromatics of the chocolate escape if they don't have good barrier properties).