Rim tape lasts forever, provided you don't have sharp spokes or burrs constantly rubbing again it (rare) - that's why I'd do a quick sanding first just to make sure. Rub a finger around the rim; anything sharp or bumpy just file/sand/rub down. Other than that, the only time you may need to remove the tape is if you're replacing a spoke or something.
The only other thing is to buy the right sized width tape. For a 305 rim, you'll have plenty of tape left over. Maybe you'll be able to use one roll for two wheels. No guarantee though.