As noted above the heads up for if they are developing into maturity, they will probably fight.
It would be very unusual if they just got along all the time through the rest of their lives. Keep an eye on them, to be sure. You could possibly come home to a near dead or dead fish when the hormones start flowing.
Some times in a very large tank, they can have security in their territory personal space so to speak, but there is a very real reason they are referred to as Siamese Fighting Fish.
When the fish are younger, they often are kept in juvenile groups in one large tank. As they begin to age they are changed to the individual containers for safety.
Be vigilant for aggressive behavior.