The time or distance an electric bike battery will run between chargings is impossible to judge with much accuracy. There are too many variables: terrain, speed, rider weight, bike load (shopping, kids, luggage), and more. However, we can make a few generalizations about an e-bike’s recharge time and overall working life. These generalizations should be used for comparison purposes only.
You should also think about how much gear you are going to need to carry. The reason this will affect your decision is because some electric bikes don’t have the capability to mount a front rack while others do. Plan on doing a 3-day trip? You could probably get away with just a rear rack. My advice though would to be to purchase an electric bike with the capability to mount a front rack as well. This way, if you decide to plan a longer trip in the future, you can simply buy a rack and be on your way instead of potentially having to buy a new bike.
For many bikes, battery range is more important that total power (because they're all pretty powerful). You want a bike that delivers a range long enough for your rides at the power levels you want. Most e-bikes will have three to five levels of assist kicking in anywhere from 25 percent of you pedal power to 200 percent boost. Consider how fast the battery takes to recharge, especially if you'll be using your bike for long commutes.