If you get any billet higher that Candidate Officer LTJG, you have done something wrong. I honestly did at most 2 hours of total work throughout candio phase. It was like summer camp with more sleep and booze. Also, I never felt bad for thoes who ended up with responsibility while at OCS. Call me a slacker, but whats the point. Everyone ends up an Ensign anyway. Take thoes last 3 weeks to put that weight you lost back on.
Back in the day at AOCS, everyone got a reserve commission, except those whose NSS scores qualified them as Distinguished Naval Graduates, and they were offered a regular commission. I think that it worked something like this: if your final AOCS NSS was in the top 10% of the past 10 graduating classes, you were a DNG and got a regular commission. Other than personal pride and motivation, that was a reason right there to always do your best and try to finish high in your class.