Well - heaven is a place of peace, but also a place where conflict can take place, albeit on a minor scale. We know from Ezekiel 28 and Isaiah 14 that the “Morning Star” (Satan) confront God in the heavenly realms and is cast out. There is an example of conflict for us. This conflict is not enough to change the character or nature of heaven, but there was conflict. Secondly, this conflict doesn’t imply that God and His nature was at risk. God was/is superior to all angels as He created them and directs them. Satan’s challenge to God was bound to fail from the start. But there was a conflict. I think a lot of our images of heaven (though not all) come from popular images of heaven from popular culture. What we do know is that God’s rule is perfect peace and where He is so peace is ruling, but not without challenge.
The “war” we see in heaven in Revelation 12:7-9 is a parallel to what we see in Ezekiel 28 and Isaiah 14. It is the site for the final rebellion and the final victory of God. To my knowledge, from my understanding of Revelation, this war mentioned in Revelation 12 is the only one that occurs. So could it happen again, according to the Scriptures and its accounting of the final days, it won’t. That being said, war in heaven doesn’t change its nature as a place where God resides and He is peace. Further, the Father is joined by the Son at His right hand - the prince of peace!