Anectodal evidences suggest that is does not hurt and in fact it could help. Furthermore, you can check your "checked-in" flight approximately 4 hours prior to departure online to check if you have been lucky. No upgrades takes place unless flight is fully booked, and it is absolutely neccessary.

What makes difference is your status, not "how early/late" you checkin, unlike some third world carriers (eg. a bankrupted airlines from arrogant country ring a bell? )