Grab another device and install Summoner's War onto it.
Use a different account for the 2nd one.
Don't think you should do this though since there's no way to trade monsters or runes.
You'll most likely end up with a really good monster on your spare account and wish it was in your main. Then you'll decide that since they're both yours, you'll make the spare account your main account and the main account your spare. Until you suddenly summon out a monster you've always wanted on your previous main account. Now you're stuck at a dilemma and your solution is most likely to make them both your main accounts. Except juggling two main accounts isn't as fun as just enjoying one account, so you'll end up losing interest in one of the accounts or both.
I say stick with 1 account and just find something else to do while waiting for energy to recharge.