I printed many of your replies to this thread and marked my book for relevant rules...
Great great hints. What I decided to do was wait of course to use chase rules until the distance is closed and paid more attention to decisions made about forced marches, travel pace and watch at night and so forth. Tracking is important.
My group is very cautious! Right out of the gate, they let the bad guys get a 3.75 mile lead and have chosen to take a normal pace. The bad guys took a fast pace slowing on the second day assuming they were in the clear or that the dangers they sent out would kill the party if still pursuing!
The players did some fun stuff in their very cautious way. caltrops in a choke point leading to their camp meant stealthing bugbears could not swarm in with impunity! The best part? The caltrops were part of a hazard in the dungeon that they took the time to collect and bag.
The variables and choices are fun. The characters are pursuing the bad guys but collected an item from their evil cathedral (and evil magic stone). Creaturs were warped in the cathedral (via the evil stone). the characters collected it and the evil creatu s warped by it are drawn to it....and so as the characters pursue the bad guys via tracking, they are in turn getting attacked regularly by The warped creatures who were commanded to do so (they have an innate sense of where the stone is)! The bad guys ordered its recovery and they can sense and are drawn to it.
The bad guys are running to their leader which the characters would never guess or find except for the slower pursuit. Faster like I thought and they would fight the bad guys well short of the big evil in the dead lands to the north!
It's turned into a bloody cannonball run which is really wild and totally dependent on what the party chose/chooses! Every group is being pursued by another...
But should the party get close, I have the rules grokked and ready for a closer chase of their quarry.
As they go, the waves of enemies are getting stronger--if they don't pick up the pace--but hey it's their choice.