When I went to UBI bike school some years ago, one of the instructors there said he had worked at bike shop in Chicago for years, where he became the expert handlebar taper. He said there was an old Polish guy, a former track racer, who used to bring his road bike into the shop once a month or so for new white bar tape. The job had to be just perfect or the customer would make him do it over--which was tolerated because the guy spent so much money at the shop. Stressful, he said, but it did teach him how to tape bars just so.

Personally, I don't replace bar tape until I get a registered letter from the Vermont Board of Health telling me that I have to.