Yes, I always have the automatic render output enabled, and set to compressed TIF. BMP is just a terrible, terrible format. Don't use it. Seriously.
![Wink ;)](https://www.planetside.co.uk/forums/Smileys/fugue/wink.png)
Anyway, if auto render output is enabled, then little mistakes like hitting Render again aren't a problem, mostly.
- Oshyan