Jsparla's reply was informative.
I will suggest one exercise; to pick out a number of relatively unpleasant materials, that are nonetheless used in perfuming, and practice making blends with those. Those provide lessons about tracking "fade", as the immediate impression upon adding the correct dose is not always as pleasant as it should be (correct me if I'm wrong, as I am typically just speaking from personal experience, unless otherwise indicated).
I love "ugly" top notes, like tea tree, menthol, and camphor, in that respect. These are good to study.
Summer savory or thyme would be a good one to experiment with here, as these are so strong and interesting, they are either going to fade and make the whole thing more interesting, or dominate with their own patterns. You have to find out which.
Sulfurous notes are another intetresting exercise I could use myself.
Cumin is great that way. Track it. Similar to nutmeg, as you mentioned.
Geranium and lavender have a strong immediate efffect, which is interesting to track.
The number of base notes with interesting time effects are numerous. Valerian is a fun experiment, or costus.
Aftel once wrote, "nothing prowls through a mix" like civet. For me, she was talkiing about all animal products.
As you say, some receed with time, some dominate.
In many cases, as David would remind us, this is because every natural substance is a collection of aromachemicals with their own rates of evaporation.
As with life, ugly often becomes beautiful with time. On the other hand, I was always told beauty is only skin deep whereas ugly is to the bone. So what do I know? Father time is beating me with an ugly stick as we speak, and I will report back when I figure everything out... :)
So as David says, you have to get to know the materials. Learning about perfume making involves exercises and studies. In practice, you get curious about an idea, and sit down with odorous substances.
For me, it often happens when I read about a funky note, like say spikenard, and you think, "what could be going through someone's mind to want to use this stuff?" I wonder that about every funky or pungent or dominant note, similar to the folks here who sustained a long thread on "skunk". So it's fun to track these.
Another kind of "funky note exercise" would be to take one such overly interesting note, and combine it with several relatively neutral substances, say benzoin, linalool, lemon, sandalwood, rose, and galaxolide, to invoke a mix of top, mid, and bottom notes. Make six vials mixing your chemical of interest with each of those substances, using suitable dilutions. Make notes on each substance as regards time effects this way, as one way to study it.
Edited by DrSmellThis - 7/3/13 at 4:41am