Being a perfectionist, this bugs the hula hoop out of me, too. I remember when I finished my Sandcrawler, I noticed something wasn't quite right. A quick look at my booklet showed that I mixed up a bunch of the bley and black pieces. I had to basically rebuild the whole thing, again.
I think the best remedy for this problem is to only build during the day, preferably with a movie, and to always take short brakes, so your eyes don't get all fuzzy. (This also prevents scoliosis. Take it from someone who has to wear a back brace every. single. night.)
They're all wasted!