It seems that NewsBin Pro uses a memory caching system that will try to decode and reassemble the file completely in RAM and therefore only write to the disk once (as a finished file), for downloads that occupy less than 100 blocks (approx. 70MB?) The frequency of hard disk writes is not adjustable, for reasons of trying to keep preferences setting simple by avoiding complex advanced-user settings. But the non-adjustability of disk-caching is something that dialup users and those with crash-prone PCs obviously are not going to be happy about.
http://forums.newsbin.com/viewtopic.php?t=18986(I actually prefer the concept of keeping two sets of settings: the advanced settings - especially settings that inexperienced users could cause harm if badly chosen - available only by manually editing the configuration file, and GUI "tickbox" settings that make it easy for beginning users to understand, by not throwing out too many choices that might only confuse them.)
... if only I'd known about NewsbinPro's RAM caching feature before my last hard drive died using Grabit