Great news!
By the way, my old ABS project in rpg maker XP used a custom pathfinding script I made. It was lag-free, because the pathfinding script did't run in one frame, instead it was spread out for a maximum of 3 seconds (120 frames)
The monster would use the built in approach when he has no Path to follow, request a Path eventually, and follow that. The path only gets reseted, when he is close enough (visible on the screen), so the pathfinder wont always run (saving performance), and the player won't notice that.
Now, I just need to find that project, and try implement the script, if you are interested :D
Edit:
I found it!
Edit2:
I implemented the script, it finds the path, and generates absolutely no lag. If you are insterested, I will upload it somewhere.