I keep mine outside simply because they have more space out there than they ever would have inside. And because of Molly's hocks, I can control her flooring much more than if she was inside. Imagine covering the whole floor of our house with hay, just isn't practical. :shock: Maybe in the future, I'd have indoor rabbits, but not now.
And outdoor rabbit's lifespan shouldn't be any different to indoor rabbits, as long as cared for properly.