I voted sometimes. It depends on what I'm doing. If I'm burning it and shifting at 13k, then I'll lay off the clutch. It's so much smoother to toe the shifter, and blip off then on the throttle. Slips right in and the only indication you shifted is the lower revs. BTW, that's how 99% of auto transmissions work.
Also, if I'm burning it, I'll work on my engine brake downshifts. You'll use the clutch just long enough to slip the gear. Pull the clutch in and blip the throttle, knock it down a gear, let the clutch out. If I'm just slowing down normally, once the revs are below 4k I'll just tap the bike down a gear. Throttle is already zero then, so again all you notice is the revs jump up.
Unless you tottally lose count and do that into first. Then the rear locks for a second and the bike bitches. Shifting under load will wear it down faster, sure, but when the tranny isn't loaded, shifting clutch in or clutch out is all the same to our tranny. Putting a bit of pressure on the shifter, but not enough to actually shift, and then rolling off and on really quick will allow the drive gear to slide down during that brief moment between the engine turning the shaft and the rear wheel turning the shaft, and that's just about as easy on the gears as you can get.
When you use disengage the clutch it only removes the engine side from the drive shaft, the wheels will still be turning the tranny over. Ever lazy-foot it and grind going into second or down into first? That's why. Tranny is still turning even with the clutch in (disengaged), the load is just much less.
Now from what I understand, the double clutches are different, it clutches both sides? So that might be a different story there.