As others states: don't count on courtesy upgrades at all. Bid, if you want the comfort (and earnings).
In 4 years as EBD I had 2 courtesy upgrades (from PE to biz (one for 2 pax, the other for 4 pax). Last one was this January ORD-CPH on an A330. PE was almost empty in advance and biz was less than half, so it was really a courtesy upgrade, not something they 'needed' to. (in the end bizz was full).