Ever get one that tastes like coca cola? That's just a mix of many different artificial fruit flavors, near as I can taste.
If you really like a certain flavor, how do you ensure it doesn't shift with the next harvest?
You don't....
Each harvest is unique. Some years are better than the next. Last year's and this year's crop out of Brazil are stunted due to frost and drought.
But....I happen to like blended coffees. Where two separate types of beans are chosen for particular flavors....roasted separately to bring out certain features and then blended and ground in proportions. That tends to provide a stable flavor one year to the next.
My current favorite is a Nicaragua and Guatemala blend that I developed.
The Nicaragua has the "burt tire" chocolatey bitterness and the Guatemala has fruity, wine like flavors of blackberry and flowers. Together they make a complex and balanced cup of Joe that is unique. Really good stuff.
Your Starbucks takes a institutional type harvested bean (machine picked instead of hand) without a lot of unique flavor and blast dries them then roasts most of the flavor out of the beans. (Burnt tire) and then grinds and serves the finished coffee....not a lot of unique flavor, smell. But it's consistent.