In the episode "Force of Nature" the idea was introduced that warp travel was damaging the fabric of subspace, with subspace rifts appearing near Hekaras II, so the Federation decided to limit Warp travel to warp 5 unless there is a emergency. However I wonder if that didn't put a limit on story telling and it seemed like it was just ignored later. During the Dominion War, Dominion ships would have ignored this limitation and Federation ships would have to go as fast as Dominion ships in order to counter them. So it seems like these limits were soon ignored. So was putting limits on Warp travel a bad idea?