Not all wines open up with air. Fruity and inexpensive red and white wines taste best when they are first opened. All wine goes bad with enough exposure to air. Wines intended to age in cellars and develop earthy or savory flavors can improve with a few hours or even a full day of exposure to air before they decline to tasting awful. Inexpensive wines often have an even shorter time they are good before they descend into undrinkability. I’ve had good, cheap wine (I’m talking $4 or $5 cheap) that tasted great when I first opened the bottle, but had lost all of its deliciousness after 30 minutes and toasted downright bad within an hour. Conversely, I’ve had more expensive wines with complex earthy and savory flavors that got better throughout the night, and a small amount I saved for the next day tasted just as good or better.
So what does all that have to do with aerators? Aeration speeds up that process. Aerating a wine can make a wine you just opened taste like it has been open for 30 minutes, one hour, two hours, or more. This can be good or bad depending on the quality of the wine. When I open a bottle and consider using an aerator, I always pour two glasses—one sample straight from the bottle and one sample through an aerator. I decide which tastes better and do that for the rest of the bottle. The unaerated sample often tastes better.
What about white wine? It’s up to you, but I don’t aerate white wine. It may help white wine meant to age for years and develop savory or earthy flavors, but I drink mostly light, crisp, fruity, and refreshing white wine – a style best enjoyed fresh and unaerated.