If you're getting this fairly often:
New block detected, possible missed longpoll, flushing work queue
Does that mean you should reduce the scan time? If it's not too often, is it okay to just leave it be?
I'm on slush's pool, which I think doesn't support longpolling, so seeing the message doesn't surprise me.
That's a harmless message that you need do nothing about. It means the automated new block detection which I implemented for cgminer is detecting the block before longpoll is telling it there's a new block. It also means that longpoll is activated, but auto detection is beating it. If longpoll was disabled it would have just said "New block detected, flushing work queue".