Do you ever purchase singles?

Absolutely, I honestly have such a hard time liking a song these days that isn't one of an artist's popular singles. My rule of thumb is, if you like a song by an artist that actually isnt one of their primary singles, then I'll consider buying an album. Because I treat it like that, I've never been too unsatisfied with an album I bought.

Anyways, you like what you like, just because really like one song by an artist doesn't mean you should try and like they're other stuff if you don't. If you think an artist is interesting enough to be worth it, then do it. Otherwise it's a waste of time.

All the time, usually with some specific bands such as Linkin Park, Pink Floyd, etc.