This will definitely not be my last word on this topic, only the beginning.
Though I’ve been doing forum RP off and on for . . . about eighteen years, I have only really ever considered how it affected my productivity, both positively and negatively. Overall, writing in general tends to increase my emotional and mental ability to write. However, too much RP can lead to burnout or focusing too much on RP because others are expecting a response and I feel the pressures of time.
And drop RP for a time.
I find that RP writing is really useful for character development, though, and considering how one’s characters will react to something outside themselves. Though I have very little control of my own characters, there are times when writing my own can seem designed and directed entirely by the author (aka, myself) and not natural to the characters themselves. Though I don’t often try to RP characters for works-in-progress, just because they’re my own personal . . . created entities.
Recently, though, I developed a character for my friend’s D&D campaign set in her modern fantasy setting. And realized that the character, Andrew, could also exist in my own universe with only moderate alterations. We did some pre-campaign RP for him, and her protagonist, and I found it really useful for developing the character. Which I then began writing a story for . . .
It was also just a lot of fun.
The RP is posted here on Anne’s blog, if anyone’s interested in checking it out: Bloodlines Roleplay