If you use a set that caps out at 35 then that is the highest the bonuses from the attuned enhancements will scale. Sometimes it is worth using some lower level enhancements when they give set bonuses a build uses, especially if you are already hitting scaling caps on important features. IE a lot of DMG sets push hard into the red on DMG at higher levels, and the lower level sets often compromise on accuracy, which is often a minor concern for SoAs given all the ToHit and accuracy bonuses they can get elsewhere.