when to stop

[BlackSTX]

Not really, though it depends on what mods are being considered. Obviously one isn't going to be slapping serious mods into a vehicle that is high mileage and is well worn; you'd only be bringing about it's expiration date a bit sooner. That being said, my friends and I have not hesitated to put parts on vehicles that had some mileage and sat in the field for ten years. Of course, this was after all fluids had been changed; calipers, carbs, plugs, cap/rotor, wires, had all been changed/rebuilt and vehicle had been driven a while to determine its condition and reliability.