I had a private sessions with a national-level IPSC competitor, and he did tell me it is best to practice using the sights all the time, to the point where it is subconscious. We did some drills (El Presidente, with three silhouette targets at like 5 yards away). After some pretty good successs I made a comment about barely even remembering looking at my sights, and he said it is probably because I have good natural aim, but that won't cut it at even slightly longer ranges. He then set up two ~8" steel targets another 10 yards back in between the silhouettes (about 15yd total for those), and told me to shoot those after the silhouettes. Of course, even though I made A-zone hits on the silhouettes apparently not looking at the sights, I missed the first shot on both gongs and had to more carefully re-aim with the sights for the second shot. Had I been in the habit of using my sights the whole time, it might have taken me a split-second longer for the silhouettes (at least until I get better, because obviously he was lightning quick compared to me and still reports always the sights), but I wouldn't have missed the further targets. However, my biggest shock was really that my brain didn't automatically switch from point-shooting to sight-shooting as the distance increased, since I always imagined it would.
All that said, I probably would still-point shoot in a quickdraw SD situation out of pure instinct, and I do think it is a good skill to practice so you have that tool available when you've got 1 second to hit the two threats standing 3 yards in front of you.