It depends on how the tape looks, how dirty the car/tape gets from track conditions [on the exposed adhesive sections], and how often you remove/change batteries.
All that said, I'll reuse the tape 3-4 times before I change it. Obviously, if there's any tearing where the tape passes back up through the chassis, or dirt is keeping the tape from sticking to the battery everywhere it should be, I'll change it out sooner.
Also, if you're prone to hitting things hard and often [like I am from time to time
], you can usually fit a second strip of tape through the chassis slots to secure the battery with about 1/2 tape width over lap for a little extra insurance against the battery coming loose.
Close fitting lipo stops will also alleviate some strain on the tape, if you have that option.