If you’re not going to animate, who cares if its got some tris.
It is not just about using quads, it is the flow of polygons in the mesh. For example, a body made for animation is not just made out of quads in any old random order, it has the correct topology to allow the limbs and body to bend and move without distortion.
It depends on what you’re doing - if it’s a subdivided model, stick to quads (image), but that’s for completely different reasons. For animation, it doesn’t matter as far as I know, as long as you keep the loops (and they don’t have to be recognised by Blender as loops). Here’s a model from Gears of War. It uses tris in all sorts of difficult-to-animate areas, like the mouth, shoulders, knees and wherever they help the silhouette.