If it took bp that long to clean up the oil spill how long would it take scientists to prepare for an asteroid?

Scientists are already preparing for an event like this to happen. They suggested destroying the asteroid using nuclear weapons, but that would ter the asteroid into millions of pieces.. essentially making the asteroid even more dangerous. I'm guessing it would take at least 20-30 more years to prepare for an asteroid... There's no way in hell we have any sort of technology to stop an asteroid. Also, if a comet hits us now, we're ALL screwed.