Where is the anime convention at, and what will the weather be like at the convention? If it's going to be hot, sunny, and humid at all during the con, then you should wear the partial on and off throughout the day. Maybe 45 mins. to an hour on, then 30 mins. off.
But like I said, it all depends on outside weather and/or other environmental conditions inside any buildings you're at. The hottest part of a partial suit is going to be the head. Drink water and take breaks. It's not uncommon for other full or partial suiters at furry cons to walk around without their fursuit head on. I've seen it done many times. Some people simply can't get to a headless lounge so they'll take their head off and walk around for a while to cool off, or some people take the head off as it's easier to chat with others, or there could be other numerous reasons. If you need to take the head off and don't want people to see you or take your picture, then find a alcove or other secluded spot where you can dehead and rest.