Not indoors unless it is somewhere with an abundance of natural lighting. Yes, you are a dbag for wearing them at night. That scene in topgun was really gay, but aviators are a classic and as long as you have the face for them, they look pretty good.
edit: Paul, Oakley does have excellent quality sunglasses. I have been wearing them for years (they have military grade ones) and they haven't failed me. I do agree though on the ordering online part. It is really hit or miss, it is best to find a retailer and try them on.
I've got RayBans and love them. Good quality and classic style.
Only times I wear them at night are to fun parties with friends. Women love them and always ask to try them on. It's funny until the fifth person asks, and then you start to worry about someone walking off with your $100 sunglasses (that's when they get put away).
As for different styles, sure you can go that route. But sunglasses are more of an icon for yourself. Everyone knows you always wear that sweet pair of (Oakleys, Maui Jims, Ray Bans etc). That is, unless, the style is too focused (such as sports sunglasses or fashion statement sunglasses).
The Top Gun scene? That was, like, one of the best scenes. And that song, Playin with the Boys, so hot. And Val Kilmer is so dreamy in that movie.
I wear Native. Specifically the Ignition. It's important when buying sunglasses that they fit your face. I have a small head and narrow face, and the Ignition is a perfect fit for me. That's one thing that I love about the good sunglasses is that they will list the frame size most of the time, and you can know if you will get a decent fit out of them. Had my Ignitions for going on 4 years now and they are still in perfect condition...Well I have noticed that one of the ear pieces seems to have more play now, but hey, it's been 4 years.
I will find myself sometimes wearing them inside, but usually just because I'm running in to grab a bottle of water or something. Anytime I'm inside for extended periods of time they are off. Never wear them at night.
Never inside, never at night. I think you should have a casual/dress pair (when wearing a suit or going for a stroll) and a sport pair (when cycling, running, or doing whatever else). Pick glasses that you feel comfortable wearing and that aren't a bright color.
Volleyball scene is quite awesome