I don't think I have ever scratched a board thru normal use, only if it is dragged across a rock or something on the beach or careless handling at home / loading in the car. With a quality bag and only ever laying it on sand or grass I don't see the issue.
By the time it looks tatty you probably want another one anyway....
Justins example of how hard it is to remove rail tape is why repairers charge a lot more if they have to deal with that issue. It is annoying to get it off do a repair then reapply. For SUP I would never tape the rails, just do electrical tape around the paddle blade properly and your board will be fine.