Monoprost 50 throw away or use again

I take them for 3 months now, one drop for every eye, every evening. The package insert states that you should discard the opened vial after use. My eye doctor, however, said you can use it again within 24 hours. How do you guys handle this? You can definitely put the opened cap back on the vial, so surely you can use it again? If so, how should it be stored?