If yo get the cellular model, you might want to turn off cellular access when you are doing longer training runs. My series 2 lasts about 5 hours of exercise on a charge. The linked runners world article inly got 3 hours. I'd bet that the difference is the cellular access.
Also, the Nike run club app will be updated soon and it's supposed to include some traInning programs built into the watch so you might want to check that out once it updates.