You want to change your life in painting a large room or maybe an entire house? Invest in 18-inch rollers for walls and ceilings, along with a paint tub, grid, and disposable tub liners to match. The first time I watched a professional painter use one of these (I had never seen one), I was flabbergasted at how much faster the job went.
There are some things you need to know, however.
A. Reserve 18-inch rollers for big jobs. They are best suited when you have more than one room to paint and clear working space.
B. You should know that these are more tiring to use than 9-inch rollers, particularly when it comes to painting ceilings.
C. Like rolling any surface, good technique counts. Stand far enough away from the wall so that when your arm is fully extended (using a paint pole) there is no danger of the roller making contact with the ceiling. Start in the middle of the wall, roll up, stop, roll down, then move on to the next stripe. Finish by taking overlapping passes, only downward.