If your non-GUI threads are processor bound they will consume as much of the processor time as they are allowed by the OS and that will impact on any other processor bound thread such as your GUI thread. By chucking in some "down time" in your processor bound threads you give other threads a chance to get some work done. Probably 1 second is excessive. Most likely you could reduce that to 1ms and still have a responsive GUI thread without impacting the processing threads much.