Every wargame enthusiast feels an urge at some point to participate in a huge battle. Such an event is something nice to have experience participating in but ultimately it is the stuff the dreams are made of - not something you really want or need in your life. Nevertheless I will give you a survival guide should you go for it.
The most important rule of huge battles is not to have fun — it is practically impossible in such mental and physical stress — but to have great stories to tell and pictures to show. So prepare some great cameras and lighting and prepare some cool handouts like certificates of participation that will push the players and spectators to forget the toil and boredom and focus their memory of the achievement of having played in a huge battle.