Hmm...I'm surprised also at the advice people may give about going from Ubud to the airport. It's only about one hour to 90 minutes unless there is a really unusual thing happening. I remember once the presidents of the USA (President Obama who is wildly popular here), Indonesia and another country were making an announced trip to Ubud and I had a flight leaving early afternoon. We decided it would be horrible traffic so left 2.5 hours for the trip and make it in about 1.5 hours.
It may also be that people saying this dont' really know where Ubud is located and think it's somewhere much further away or in difficult topography or are even just repeating what they hear or read somewhere else. The only thing I could think of is if your flight leaves on the night before Nyepi March 22 when there are indeed parades going on. But those are usually not blocking major roads to the airport so it shouldn't be an issue.
But in any case you will be perfectly fine...enjoy the end of your trip in Ubud!