That is what I understand. Above 70W and you risk burning out your wiring harness. Above 70W you should use an auxilliary wiring harness. Sold by Auto Dynamic (.com) for $35. Very complete and not TOO much of a bear to install. Still the right thing to do.
As already stated, less than 70 watts when using the OEM wiring. With an aux harness and relays you may use 80 - 100 watts. I have been using an 80 watt low beam upgrade for over 5 yrs using the aux kit without any problem.