Technically you can, though I prefer not to, as you run the risk of overcooking the yolks when reheating them. However, if you do want to, I recommend storing any cooked and cooled (use an ice bath) poached eggs in an airtight container in the fridge for up to 3 days. Add the eggs to a mug/bowl with boiling water to reheat them. They should be warm within 30-40 seconds.