I would want to replace it at that point anyway worn or not. Tape soaks in your sweat and it sits on the handlebar all the time and you cannot see what is going on underneath it. It is a good thing to do yearly and you can also replace cables and housing and get better shifting and braking as well.

I have seen a few handlebars that have white powder (corrosion) on them and that is not good and poses a safety risk. Tape is pretty cheap and easy to find at any bike shop just about anywhere and it also can make your bike look really good so it is good to replace regularly for that reason as well.