cracks in the rubber look like they're almost fully thickness of the belt in places this belt is probably not long for this world now.
its not just about the belt snapping and you putting another one on.
you could end up stranded or worse, broken down in a dangerous position or situation. you could find the belt letting go could still cause damage to other components as a result, someone in the 500x section showed a prime example of an AUX belt breaking and taking out the oil pressure sensor. there is also the potential that if the belt is old, so it is likely, the water pump is old, that can seize and cause over heating potentially before the belt snaps. There are many more issues that can arise from a broken belt so its pretty stupid to take the approach of just changing it, if or when it snaps.