Hmm... when I feel the urge. -that said, it's pretty seldom... (maybe a few times per year) Ironically, those urges usually comes from seeing a cool rendition of a character I like, right here on dA! (However, I DO draw AVP-related stuff way more often!)
Frequently. And I don't understand why it's regarded by many as a "lesser" form of artistic expression. I'm very fond of the characters that I portray; I don't do it for some idiotic reason like "OMG i need moar pageviews" or anything of the sort.
Mostly when I'm just doodling, or when I have some random picture I've got to get out of my head regarding some characters. But I'm starting to cut down on it... Sadly, it's just my fanart related pieces that actually seem to get any attention at all.