lukulus:
Yes there are other differences too as chess is a very different game. In chess, a stalemate is a draw. In Espionage, having no legal move is a loss.
The issue on the number of moves without a capture should not be related to the overall length of a game but a reasonable number of moves for a SKILLED player with an advantage to be able to either win or increase that advantage with a capture or sacrifice.
If there is no advantage, the same rule applies (as it does in chess) to attempting to gain the advantage.
I think 50 moves is a reasonable for Open Fast.