[johan osterman]

I guess JK just picked a number. I doubt anyone have any recollection why 50/75 was picked in the first place.

If you have two immobiles without offensive spells, one teleporting in, troops on both sides routing, you would end up with an infinite amount of turns. Battles where both sides have several summoners could also potentionally Last very long. The size of the .trn files would increase as well if battles Lasted longer, if battles Lasted several hundred turns and you had a few of those your trn files would get pretty big, big enough to be a bit of a bother for players playing pbem and utilising dial up modems.