I find that feathered trebles on a hard bait are a two edged sword. They add action on the pause and simulate a living tail, but they can dampen the action if they are too long for a particular bait.
For example, for 4" jerkbaits that I move fast, I use a flashabou dressed rear treble trimmed just past the hooks, so I get a lot of action and still get flash. I don't use any feathered treble at all on bigger jerkbaits, because they are harder to work, and the feather makes them sluggish.
For 5" walking baits, I leave the feather/flashabou combination about an inch past the bend in the treble, and trim it on the water until the bait walks well. A long tail here definately dampens the walking action.
For 6'+ punker-type top water gliders, I leave the feathers long, because these big baits aren't worked fast, so the long tail doesn't inhibit their action.
For sub-surface lures, I tie the feathers long, and trim them on the water if they slow down the X'ing I want.
For me, my general rule is the smaller the bait, the smaller the dressed treble, and the faster the action I'm looking for, the shorter the feathers.