I got tired of making #'s with race tape at road events so I had sticker #'s made by a printing place with "less sticky" adhesive. When I was at Road Atlanta for a NASA weekend event there happened to be a cruise night at YEAR ONE down the street Sat. night so we decided to go check it out and took my car. The whole crowd turned and stared as I rolled in! then I realized it must be the #'s that were still on the car!
So now I run them as well the other stickers (windshield banners etc.) on the street for a short time after an event. Then when I want a more subdued look or more elegant look I take them all off.