How many times must you purchase the safe now that the coin/experience doubler purchase is no longer..

How many times must you purchase the safe now that the coin/experience doubler purchase is no longer available? I’m a bit confused and very curious. Do you need to spend the {$4.99 USD, for example} for each and every single time you accumulate the 20k coins it takes for the safe to be available? Or does one purchase allow unlimited opens upon reaching the required 20k coins requirement from then onwards? What all exactly do you receive out of the safe/s each time that you are able to open them? Thank you for your time.