engine light went off by itself?

Last week I had my engine light come on, and after a trip to the advanced auto, I found out that I had a bad oxygen sensor.  I wanted to replace all four 02 sensors and do a seafoam engine flush all at once so I was waiting until I had a day free so that I could devote some time to it.  However, yesterday I was driving the truck and the engine light went off, and has stayed off throughout this mornings drive.  I still plan on doing the maintanence I was going to do but I just wanted to know why/how the light would go off?  Any ideas.  Thanks     

With your mileage, your 02's arwe tired and it will come back. If you are wanting to improve your mileage and power, 02 are really going to be needed.