We have 3 years 8 days difference and my girls have shared a room since dd2 was about 11m old. They love it! Sometimes they fight about music but dd1 often goes to bed later so dd2 is already asleep. I'm sure as dd2 gets older they will have other issues lol. We have all their toys in the spare room so they share that too. They are currently 6 and 3 and the are really good buddies, play mates and sharers. They miss each other if they are not in the same room at night.