You don't need a DVR with Sling TV

Not if you only watch the History channel. You can watch the shows you missed, just not the ones that haven’t been on yet. Don’t know how many days you can go back. The best way is to watch the History channel the entire time you are awake. You can’t fast forward the commercials though, the only way you can do that, is if you pause a live show, and then unpause it after 10+ minutes. But once the show isn’t live anymore, you can’t skip the commercials anymore.