Saving an in-progress render so that it can be resumed later is a difficult thing to implement but it is certainly a well-known requested feature. Simply saving the in-progress render image at regular intervals may be possible, but it's probably not something we can implement soon. We'll definitely consider it for the final release though.
Temp files are only deleted manually. TG2 doesn't delete the temp image files it stores at this point. You may have an automated process setup that clears your Windows temp file when you restart, but that is generalized and outside the realm of TG2's functions.
- Oshyan
