I remember reading some years ago a wine column based on the theme: "If you can't afford to buy a case, you can't afford the wine." I took offense at first, but the more I thought about it, the more sense that approach makes. The idea is that you come to understand a wine not by drinking one bottle but by becoming familiar with the way it develops over time. And it's possible to do that only if you buy in quantity--whether it's six, nine, twelve or more bottles.
The downside of buying by the case is that you sometimes buy wines you don't like. That has happened to me a few times. The bottle you love in September, prompting you to buy a case, may taste very different by January, and you may be tempted to pour the remaining bottles down the sink. Novice wine drinkers sometimes assume the wine has gone over the hill, but even very bad wines generally don't die that quickly. With the exception of manufactured wines (many of which are pasteurized), wine is a living, growing thing and it will go through many changes before it reaches maturity. Some of these changes you may like; others may turn you away. But the fact that the wine has made one bad turn (for your tastes) does not mean that the next turn will be as bad or even worse. Be patient, and you may end up with a wine you're ready to commit yourself to...for at least another case.
Most Cotes du Rhone wines (which are mainly Grenache/Syrah blends) are flush with fruit when they're first released. Then they go through a stage where peppery, spicy flavors and aromas dominate. And finally, if you're lucky, they develop deeper complexities and subtleties. Some wines, of course, simply go nowhere, and those are the ones you learn to avoid. A Mourvedre-based wine, on the other hand, may go into a funky, tree-bark stage after the first year or two and linger there for several years before it blossoms like a spring flower. Cabernet, of course, is arguably the best grape in the world for aging but, in the case of great Bordeaux wines, may take several decades to reach its peak.
Every wine has its own evolution. For some that's three to five years; for others, it's three to five decades. Generally speaking, the longer and slower the evolution, the more beauty and pleasure there is in the finished product. Wine lovers learned a long time ago what those wines are and what they're worth--a lot. But even an inexpensive Cotes du Rhone or Spanish Monastrell has its own evolution, which you can follow with interest if you buy a case rather than a bottle.