last freeroll tournament i played at harrahs was like this; from 2pm-8pm every half hour 5 people to a table 10-12 tables . you play 15 hands only.start with 10,000- 15,000 in chips. 9pm top 50-60 players start with fresh 15,000 in chips. top chip leaders make the money. those that qualify had an average of 10X the starting chips.
if your tournament is something like that get the last session to see how aggressive a player you will need to be.