i'm not a cheesecake expert....but i was gonna add them to the shop a while back....i remember reading about them, that they would be kinda loose in the middle when they were done.
sorry i couldn't be more help.
I know I'm way late here but if you have an instant thermometer the internal temp is supposed to be 169 degrees. My local grocery store sells the therms for like $7. Just a thought for next time maybe.
What temperature were you baking at? Were the cheesecakes in a water bath? Since I'm late with this, how did they turn out?
I made cheesecake yesterday. My recipe is for a 9" in a springform pan with 1.5 lbs of cream cheese. I baked for 1 hour at 350F.
Hope yours came out OK 
!
If you have baked for 4 hours, that's WAY too long...unless they are 16" diameter and 8" thick! Cheesecake should have a "wet spot" in the center even when it's done. It firms completely upon cooling. And yeah, a thermometer would be a good thing for future reference.
Wondering how everything turned out.
4hrs is a REALLY long time for Cheesecake. 
I agree with the othe comments that it sounds like a temperature or overcrowding issue.
If you cook them until their completly firm they will be overcooked, because they continue to cook and firm up when you take them out of the oven.
Hope they turned out well.
Too many in the oven...bake them one at a time for a least 1 hour at 350.
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