I've read that it's best to delay isha namaz I was wondering exactly how long should it be delayed for?
There is an authentic narration in which the Prophet ﷺ says that he would have liked to ask his followers to pray isha at the end of the first third of the night, or at the middle of the night, but that it would have been too difficult for some to pray isha that way.
From that, people understand that it is a good thing to delay the isha prayer. You can delay it to the first third of the night or the middle of the night. The “night” is defined as the time between the isha athan and the fajr athan (not 12 AM), so if isha is at 9 and fajr at 5, that makes 1 AM the middle of the night.
It is considered sinful by some scholars to delay isha past the middle of the night, while others consider it acceptable to pray isha any time before the fajr athan.