We did Valencia - Bacolod in 51/2 hrs, starting early morning. There are still some roadworks between Himamaylan and Bacolod - no holdups in the early morning but they would probably slow you down later in the day. We came back the 'scenic route' - Bacolod - Murcia - Don Salvador B - San Carlos. It's about 70 k longer and took 7 hrs (including lunch) but I find it a much more enjoyable drive.
Not when you take the non-aircon bus that stops every 100 meters. 4 hours is hauling @ss in a vehicle. My fastest time is 3 1/2 hours on my small bike. On my 1000cc it is a little under 4 hours. (Road conditions are not optimal for a sports bike.)