Divorce is just a division of assets. You're being redundant. Live together for three years, and then divide there household, and you'll have a division of assets, which might even get litigious. Add children, and you'll have custody and child support issues, license or not. Don't do it.
Never mind that you'll turn a 6 month relationship into a 6 year "prison sentence," via inertia. It's easier just to stick together, and to work it out, because you got lazy, complacent, or put on a few pounds, and the lease isn't up, and you really like your place.
Don't do it!