It is not a stable peace if one side is plotting the best time to attack the other side.
It is if they have the slightest bit of sense about their assessment of the other side.
On one side, we have the Red Court knowing about the White Council for four or five hundred years, and taking all that time building up their forces to a point where even the most hardline of them think starting a war is a reasonable exercise.
On the other, we have Luccio in Changes noting that the Council has twice the combat strength it did before the disaster in DB. Which took them about five years.
The Council can stay ahead of any rational Red Court threat indefinitely with a much lower growth rate than they demonstrate themselves capable of. Therefore, stable.
Humans are vamp food; noone who is hungry likes it when their food gets the ability to fight back.
The most important datapoint we have here is Harry's conversation with Butters at the start of Dead Beat, which establishes that disappearances among humans in the DV are exactly the same as in reality. Harry thinks that is supernatural predation because he is not in a position to make the comparison, but the DV is shown to have crime, and abusive families, and generally the same reasons real people disappear. The message that conveys is that supernatural predation kills
negligible numbers of people.
All supernatural predation, of which the Red Court are a subset.
Which doesn't mean they are friendly kittens. But it does mean that for the White Council to spend time and enemy spent hunting them, compared to addressing much
much bigger problems (the failure mode of not catching powerful warlocks early and firmly, for example, being on record as organising a world war), is gross negligence.