This isn't sustainable. It's likely not healthy, either. It doesn't matter how fun you're having while you work 80 hours per week, it's not good for you. Most successful businesses grind away for years before they finally become profitable. The rocket-ship success stories like Whatsapp and Instagram are the exception to that rule. The whole mentality that you need to work yourself to the bone in the name of "passion" to build a successful business is poisonous. Even if you happen to be one of these super humans that can sustain that amount of work more than a year it's likely that your co-workers are not. It's also likely that they will not complain about it because they don't want to seem like the weak link. All the while, though, it will do damage to them and to the company in the long term.
Maybe working 80 hours a week is a sign that you're over-engineering. Simplify, focus, and work less. The product will likely become more focused, less bloated, and have a much better chance of surviving over the long haul.