It's not easy to predict. Some cats have got to the point where they have beautiful flat curves. Others are up and down a bit and still others are up and down a substantial amount.
Raven's only been on insulin a few months and often it takes longer than that to regulate. When you're trying to decide whether he's going up, think about when he last ate and what he ate. Food will keep their levels up usually for a couple of hours.
Like I suggested and Wendy also suggested, get a test at +2. If he's even or lower than PS, it may be an active cycle and it's wise to get a test at +3 and go from there.